Tiger Woods held on to the top spot, but his lead over Mickelson is just 0.52 average points. Woods led last week's No. 2 Sergio Garcia by 1.59 average points.
With Mickelson's move up to No. 2, Garcia slipped to third in the new rankings. He was followed by Geoff Ogilvy, Padraig Harrington and Vijay Singh. Camilo Villegas jumped three notches to seventh.
Kenny Perry and Robert Karlsson exchanged places with Perry up to No. 8, while Henrik Stenson fell three to 10th.
Jim Furyk finished third behind Mickelson and jumped six spots to 11th. Anthony Kim was down one to 12, Paul Casey held steady at 13, Lee Westwood dipped a pair to 14, while Steve Stricker, Ernie Els and Rory McIlroy each feel one spot apiece.
Stewart Cink held on to the 18th position, while Mike Weir and Adam Scott flip-flopped places with Weir up to 19th.