Lee Westwood, a runner-up in two majors this year before missing the last two months with a calf injury, will replace Mickelson at No. 2 in the next world ranking to be published Monday. The final step to No. 1 is not far behind.
Westwood will have a chance to replace Woods atop the ranking at the Alfred Dunhill Championship next week at Scotland, with St. Andrews the host course. Westwood finished second at the British Open in July. He also is expected to play the Portugal Masters the following week.
If he were to finish in the top 20 at both events, that should be enough to reach No. 1 for the first time in his career.
Woods has been No. 1 for the last 277 weeks, dating to the week before the 2005 U.S. Open at Pinehurst. He has not won a tournament since the Australian Masters last November, shortly before a car accident outside his Florida home led to revelations of multiple extramarital affairs.
For most of the year, Mickelson seemed the most likely candidate to replace him. The Masters champion has 12 tournaments where he could have gone to No. 1 for the first time in his career. But in his last seven tournaments since the U.S. Open, Mickelson has finished in the top 20 only twice.
Westwood might have gone to No. 1 except for the injury. His right calf affected his ankle to the point that he withdrew from the Bridgestone Invitational at Firestone the first week of August and spent six weeks of rest and rehabilitation.
His world ranking average when he arrived at Firestone is higher than where Woods is now. Still, Westwood is fortunate that Woods, Mickelson or even Steve Stricker took advantage of his absence, especially while playing a month of strong tournaments from the PGA Championship through the FedEx Cup playoffs on the PGA Tour.
"I'm quite fortunate in that regard," Westwood said. "Especially with the tournaments that we have been playing and with so many world ranking points available, I expected to be further behind than I am. So I'm quite pleased with the position I'm still in."
If he were to get to No. 1, how long he stays will be the next question.
Woods, Mickelson and Westwood are expected to play the HSBC Champions, which starts Nov. 4 in Shanghai.