Watson claimed his first major tournament title Sunday by beating Louis Oosthuizen on the second playoff hole. It was his fourth PGA Tour championship, all since June 2010.
Watson opened the week ranked 16th but climbed to fourth with the major tournament win. It is his second stint in the Top 10. He was in the top tier of the rankings for one week last May.
Mickelson finished tied for third Sunday and that boosts him from 14th to No. 9.
Donald has a ranking points average of 9.614, not far ahead of Rory McIlroy, who is at 9.531 after ending up tied for 40th at the Masters. Lee Westwood, who was among those tied with Mickelson for third Sunday, is third in the rankings at 8.235.
Watson's average is 6.534 while Hunter Mahan is fifth at 5.886, Steve Stricker (5.635) comes in sixth, Martin Kaymer (5.584) is seventh and Tiger Woods (5.545) is No. 8. Mahan, Stricker, Kaymer and Woods all slipped one spot in this week's rankings.
Mickelson has a scoring average of 5.307 and Justin Rose (5.276), who was ninth last week, is No. 10.
Charl Schwartzel, who won the Masters in 2011, drops from eighth to No. 12 after a tie for 50th this year.