Casey moved to No. 21 this week. Zach Johnson won the Sony Open and that boasted him 17 places to 27th this week.
The top seven remained the same with Tiger Woods followed by Sergio Garcia, Padraig Harrington, Phil Mickelson, Vijay Singh, Geoff Ogilvy and Robert Karlsson.
Only one other player in the top 20 remained in the same place from last week.
Anthony Kim and Camilo Villegas exchanged places with Kim up to eighth. Lee Westwood and Henrik Stenson inched up a spot apiece to 10th and 11th as Ernie Els dropped a pair to 12th.
Jim Furyk remained No. 13 again this week. Adam Scott shared second place behind Johnson and that helped him improve four positions to 14th. Scott's move bumped Kenny Perry to 15th, Steve Stricker to No. 16, Stewart Cink to 17th and K.J. Choi to No. 18.
Martin Kaymer shared second behind Casey and that helped him move up six spots to No. 19, while Justin Rose was down one to 20. Trevor Immelman fell out of the top 20 as he dipped two to 22nd this week.