Westwood failed to overtake Tiger Woods yesterday because he could only finish 11th in the Alfred Dunhill Links Championship, rather than the top-two place required.
But because Woods is not scheduled to play again until 4 November, the Englishman will replace him at the top of the rankings on 31 October.
And Westwood will not even have to lift a club to achieve his goal, which is as well because he intends to take at least the next three weeks off to mend his calf injury.
“I’ll take it any way,” he said. “I’ve had a great year until getting injured. Look at all the world ranking points I’ve won: I was leading that by a mile before my injury.”
The only way Woods could deny Westwood the No1 spot is by entering another tournament before his next planned appearance, at the WGCHSBC Champions in Shanghai.
Westwood added: “I’m not allowing myself to think about it until it happens. It’s something I’ve always dreamt of and it would be great if it happened.”
The Worksop player, 37, finished on seven under par at St Andrews, 10 shots behind the winner, his Ryder Cup team-mate Martin Kaymer.
His break means he will not defend his Portugal Masters title this week, where he would have had to finish third or higher to unseat Woods.