{\rtf1\deflang1033\deflangfe1033\margl720\margr720\margt360\margb360{\stylesheet{\fs20\lang1033\snext0 Normal;} {\s1\sb240\keepn{\*\pn \pnlvl1\pndec\pnprev1\pnstart1\pnsp144}\b\f0\fs30\lang1033 \sbasedon0\snext0 heading 1;} {\s2\sb200\keepn{\*\pn \pnlvl2\pndec\pnprev1\pnstart1\pnsp144{\pntxtb.}}\b\f0\fs26\lang1033 \sbasedon0\snext0 heading 2;} {\s3\sb180\keepn{\*\pn \pnlvl3\pndec\pnprev1\pnstart1\pnsp144{\pntxtb.}}\b\f0\fs22\lang1033 \sbasedon0\snext0 heading 3;} {\s4\sb160\keepn{\*\pn \pnlvl4\pnucltr\pnprev1\pnstart1\pnsp144{\pntxtb.}}\b\f0\fs22\lang1033 \sbasedon0\snext0 heading 4;} {\s5\sb140\keepn{\*\pn \pnlvl5\pncltr\pnprev1\pnstart1\pnsp144}\b\f0\fs20\lang1033 \sbasedon0\snext0 heading 5;} {\s6\tqc\lang1033\sbasedon0\snext6 footer;} {\*\cs16 \additive\super\sbasedon10 footnote reference;} {\*\cs18 \additive\sbasedon10 page number;}} {\fonttbl{\f0\fnil Times New Roman;}{\f1\fnil Courier New}{\f2005\fnil Courier New;}{\f2010\fnil Wingdings;}{\f2020\fnil Webdings;}{\f2\fnil Arial;}{\f3\fnil Arial;}{\f4\fnil LucidaHandwriting;}{\f5\fnil Symbol;}{\f6\fnil Symbol;}{\f7\fnil Ferdsch;}{\f30\fnil Myriad Cn Semibold;}{\f31\fnil Myriad Roman;}{\f50\fnil Courier New;}{\f51\fnil Times New Roman;}{\f52\fnil Arial;}{\f53\fnil Symbol;}{\f54\fnil Wingdings;}{\f55\fnil Wingdings 2;}{\f56\fnil Wingdings 3;}{\f57\fnil Webdings;}{\f58\fnil Arial Narrow;}{\f59\fnil Arial Unicode MS;}{\f60\fnil Cyberbit;}{\f61\fnil Morningstar 1U Light;}{\f62\fnil Calibri;}} {\colortbl;\red0\green0\blue0;\red127\green0\blue0;\red0\green0\blue255;\red127\green127\blue127;\red0\green51\blue153;\red255\green204\blue0;\red255\green255\blue255;\red246\green244\blue236;\red0\green0\blue0;} {\*\bkmkstart filing_1}{\*\bkmkend filing_1}{\*\bkmkstart doc_1_1}{\*\bkmkend doc_1_1}\par\pard\plain\f0\fs16\par\pard\plain\cf1\f50\fs16\ql SECURITIES AND EXCHANGE COMMISSION \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Washington, D.C. 20549 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql SCHEDULE 13G \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Under the Securities Exchange Act of 1934 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (Amendment No. 5)* \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Pioneer Natural Resources Company \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql ________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (Name of Issuer) \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Common Stock \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _______________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (Title of Class and Securities) \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 723787107 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _______________________________________________________ \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (CUSIP Number of Class of Securities) \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Check the appropriate box to designate the rule pursuant to which this \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Schedule is filed: \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql /X/ Rule 13d-1(b) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql / / Rule 13d-1(c) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql / / Rule 13d-1(d) \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql * The remainder of this cover page shall be filled out for a \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql reporting person's initial filing on this form with respect to the \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql subject class of securities, and for any subsequent amendment \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql containing information which would alter the disclosures provided \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql in a prior page. \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql The information required in the remainder of this cover page shall \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql not be deemed to be "filed" for the purpose of Section 18 of the \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Securities Exchange Act of 1934 ("Act") or otherwise subject to the \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql liabilities of that section of the Act but shall be subject to all \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql other provisions of the Act (however, see the Notes). \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (Continued on following page(s)) \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql CUSIP No. 723787107 13G \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (1) NAMES OF REPORTING PERSONS \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Southeastern Asset Management, Inc. I.D. No. 62-0951781 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (a) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (b) X \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (3) SEC USE ONLY \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (4) CITIZENSHIP OR PLACE OF ORGANIZATION \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Tennessee \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql :(5) SOLE VOTING POWER \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql : (Discretionary Accounts) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql NUMBER OF SHARES BENEFICIALLY : 11,071,907 shares \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql OWNED BY EACH REPORTING PERSON __________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql WITH :(6) SHARED OR NO VOTING POWER \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 11,201,032 shares (shared) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 3,558,157 shares (No Vote) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql __________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql :(7) SOLE DISPOSITIVE POWER \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (Discretionary Accounts) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql : 14,596,064 shares \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql __________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql :(8) SHARED DISPOSITIVE POWER \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql : 11,201,032 shares (Shared) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 34,000 shares (None) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 25,831,096 shares \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW 9 EXCLUDES \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql CERTAIN SHARES -X- See Items 4(c)(ii) and (iv) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 24.9 % \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (12) TYPE OF REPORTING PERSON \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql IA \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql CUSIP No. 723787107 13G \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (1) NAMES OF REPORTING PERSONS \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Longleaf Partners Fund I.D. No. 63-6147721 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (a) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (b) X \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (3) SEC USE ONLY \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (4) CITIZENSHIP OR PLACE OF ORGANIZATION \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Massachusetts Business Trust \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql :(5) SOLE VOTING POWER \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql : \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql NUMBER OF SHARES BENEFICIALLY : None \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql OWNED BY EACH REPORTING PERSON __________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql WITH :(6) SHARED OR NO VOTING POWER \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 11,201,032 shares (shared) \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql __________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql :(7) SOLE DISPOSITIVE POWER \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql : None \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql __________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql :(8) SHARED DISPOSITIVE POWER \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql : 11,201,032 shares (Shared) \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 11,201,032 shares \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW 9 EXCLUDES \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql CERTAIN SHARES \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 10.8 % \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (12) TYPE OF REPORTING PERSON \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql IV \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql CUSIP No. 723787107 13G \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (1) NAMES OF REPORTING PERSONS \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql O. Mason Hawkins I.D. No. 257-72-3256 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (a) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (b) X \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (3) SEC USE ONLY \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (4) CITIZENSHIP OR PLACE OF ORGANIZATION \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Citizen of United States \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql :(5) SOLE VOTING POWER \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql : (Discretionary Accounts) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql NUMBER OF SHARES BENEFICIALLY : None \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql OWNED BY EACH REPORTING PERSON __________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql WITH :(6) SHARED VOTING POWER \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql : None \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql __________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql :(7) SOLE DISPOSITIVE POWER \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql : None \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql __________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql :(8) SHARED DISPOSITIVE POWER \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql : None \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql None (See Item 3 ) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW 9 EXCLUDES \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql CERTAIN SHARES \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 0.0% \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (12) TYPE OF REPORTING PERSON \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql IN \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _____________________________________________________________________________ \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Item 1. \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (a). Name of Issuer: Pioneer Natural Resources Company \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql ("Issuer") \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (b). Address of Issuer's Principal Executive Offices: \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 1400 Williams Square West \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 5205 N. O'Connor Blvd. \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Irving, Texas 75039 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Item 2. \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (a) and (b). Names and Principal Business Addresses of Persons \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Filing: \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (1) Southeastern Asset Management, Inc. \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 6410 Poplar Ave., Suite 900 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Memphis, TN 38119 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (2) Longleaf Partners Fund \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql c/o Southeastern Asset Management, Inc. \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 6410 Poplar Avenue, Suite 900 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Memphis, TN, 38119 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (3) Mr. O. Mason Hawkins \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Chairman of the Board and C.E.O. \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Southeastern Asset Management, Inc. \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 6410 Poplar Ave., Suite 900 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Memphis, TN 38119 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (c). Citizenship: \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Southeastern Asset Management, Inc. - A Tennessee corporation \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Longleaf Partners Fund, a series of Longleaf Partners \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Funds Trust, a Massachusetts business trust \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Mr. O. Mason Hawkins - U.S. Citizen \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (d). Title of Class of Securities: Common Stock (the \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql "Securities"). \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (e). Cusip Number: 723787107 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Item 3. If this statement is filed pursuant to Rules 13d-1 (b) or \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 13d-2 (b), check whether the person filing is a: \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (d.) Investment Company registered under Sec. 8 of the Investment \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Company Act - Longleaf Partners Fund, a series of \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Longleaf Partners Funds Trust. \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (e.) Investment Adviser registered under Section 203 of the \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Investment Advisers Act of 1940. This statement is being filed \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql by Southeastern Asset Management, Inc. as a registered investment \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql adviser. All of the securities covered by this report are owned \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql legally by Southeastern's investment advisory clients and none \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql are owned directly or indirectly by Southeastern. As permitted \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql by Rule 13d-4, the filing of this statement shall not be construed \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql as an admission that Southeastern Asset Management, Inc. is the \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql beneficial owner of any of the securities covered by this statement. \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (g.) Parent Holding Company. This statement is also being filed by \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Mr. O. Mason Hawkins, Chairman of the Board and C.E.O. of \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Southeastern Asset Management, Inc. in the event he could be \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql deemed to be a controlling person of that firm as the result of \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql his official positions with or ownership of its voting securities. \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql The existence of such control is expressly disclaimed. Mr. Hawkins \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql does not own directly or indirectly any securities covered by \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql this statement for his own account. As permitted by Rule 13d-4, \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql the filing of this statement shall not be construed as an admission \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql that Mr. Hawkins is the beneficial owner of any of the securities \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql covered by this statement. \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Item 4. Ownership: \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (a). Amount Beneficially Owned: (At 12/31/01) \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 25,831,096 shares \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (b). Percent of Class: \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 24.9 % \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Above percentage is based on 103,900,000 shares of Common \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Stock outstanding. \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (c). Number of shares as to which such person has: \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (i). sole power to vote or to direct the vote: \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 11,071,907 shares \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (ii). shared or no power to vote or to direct the vote: \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Shared - 11,201,032 shares. \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Securities owned by the following series of Longleaf \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Partners Funds Trust, an open-end management \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql investment company registered under the Investment \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Company Act of 1940, as follows: \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Longleaf Partners Fund - 11,201,032 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql No Power to Vote - 3,558,157. This figure does not include \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 731,300 shares held by completely non-discretionary accounts \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql over which the filing parties have neither voting nor \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql dispositive power and for which the filing parties \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql disclaim beneficial ownership. \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (iii). sole power to dispose or to direct the disposition \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql of: \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 14,596,064 shares \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql (iv). shared or no power to dispose or to direct the \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql disposition of: \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Shared - 11,201,032 shares \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Securities owned by the following series of Longleaf \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Partners Funds Trust, an open-end management \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql investment company registered under the Investment \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Company Act of 1940, as follows: \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Longleaf Partners Fund - 11,201,032 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql No Power - 34,000 shares. This figure does not include 731,300 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql shares held by completely non-discretionary accounts over which \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql the filing parties have neither voting nor dispositive power \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql and for which the filing parties \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql disclaim beneficial ownership. \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Item 5. Ownership of Five Percent or Less of a Class: N/A \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Item 6. Ownership of More Than Five Percent on Behalf of Another \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Person: N/A \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Item 7. Identification and Classification of the Subsidiary Which \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Acquired the Security Being Reported on By the Parent \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Holding Company: N/A \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Item 8. Identification and Classification of Members of the Group: \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql N/A \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Item 9. Notice of Dissolution of Group: N/A \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Item 10. Certification: \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql By signing below I certify that, to the best of my knowledge and \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql belief, the securities referred to above were acquired in the \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql ordinary course of business and were not acquired for the purpose \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql and do not have the effect of changing or influencing the control \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql of the issuer of such securities and were not acquired in \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql connection with or as a participant in any transaction having such \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql purposes or effect. \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Signatures \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql After reasonable inquiry and to the best of the knowledge and \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql belief of the undersigned, the undersigned certifies that the \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql information set forth in this statement is true, complete, and \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql correct. \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Dated: February 4, 2022 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Southeastern Asset Management, Inc. \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql By /s/ Charles D. Reaves \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _______________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Charles D. Reaves \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Vice President and General Counsel \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Longleaf Partners Fund \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql By: Southeastern Asset Management, Inc. \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql /s/ Charles D. Reaves \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _______________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Charles D. Reaves \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Vice President & General Counsel \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql O. Mason Hawkins, Individually \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql /s/ O. Mason Hawkins \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _______________________________________________ \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Joint Filing Agreement \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql In accordance with Rule 13d-1(f) under the Securities Exchange Act \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql of 1934, the persons or entities named below agree to the joint \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql filing on behalf of each of them of this Schedule 13G with respect \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql to the Securities of the Issuer and further agree that this joint \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql filing agreement be included as an exhibit to this Schedule 13G. In \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql evidence thereof, the undersigned hereby execute this Agreement as \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql of February 4, 2002. \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Southeastern Asset Management, Inc. \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql By /s/ Charles D. Reaves \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _______________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Charles D. Reaves \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Vice President and General Counsel \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Longleaf Partners Fund \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql By: Southeastern Asset Management, Inc. \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql /s/ Charles D. Reaves \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _______________________________________________ \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Charles D. Reaves \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Vice President & General Counsel \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql O. Mason Hawkins, Individually \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql /s/ O. Mason Hawkins \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql _______________________________________________ \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 1 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql PXD13G5.doc \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql SCHEDULE 13G - Pioneer Natural Resources Company ("Issuer") \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql Amendment #5 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql 9 \par\pard\plain\fs16\pard\plain\cf1\f50\fs16\ql PXD13G5.doc \par\pard\plain\fs16 \par\pard\plain\fs16 \par\pard\plain\fs16}