Lee Westwood is set to replace Tiger Woods at the top of the rankings on Oct 31 after saying on Sunday he does not expect to play again until November because of an ankle injury.
The Englishman will go top if he does not return before the end of the month and Woods continues with his intention not to play again until the HSBC Champions event from Nov 4-7.
Westwood has been struggling with a right ankle injury and finished joint 11th at the Alfred Dunhill Links Championship won by Germany's Martin Kaymer.
Asked when he might play again, Westwood said: "At the earliest probably HSBC, maybe Dubai (Nov 25-28)."
Woods has topped the rankings for over five years, since the week before the 2005 US Open at Pinehurst, North Carolina. Woods will have been top for 279 weeks in the rankings published on Monday.
Westwood said his injury had been troubling him for a while.
"I haven't had a chance to get it healed," he said. "Tried my hardest to get back to the Ryder Cup fully fit last week and got back to 80 percent, which I thought was good enough for the Ryder Cup with the adrenaline and all that.
"That was a tough week back and this is not an easy week, six hour rounds and only two days off between finishing the Ryder Cup and starting here. Never going to be right, and it just got progressively more agitated and achy as the week's gone on."
Though Westwood should enjoy top spot at the end of the month, barring any changes of plan by either the Englishman or Woods, his stay there may be short-lived.
With Woods, Westwood and Kaymer, along with Phil Mickelson, playing in the $7 million HSBC Champions tournament in Shanghai, any one of the four could become No 1 in the following week's rankings.