World number one Rafael Nadal on Wednesday said he would skip the Asian leg of the ATP tour to recover from the knee injury he picked up at the U.S. Open.
Nadal's decision is set to boost Novak Djokovic's chances of ending the year top of the rankings.
Earlier, Nadal had to give in to his knee injury during his match against Argentine Juan Martin del Porto where he retired during his semi-final.
Nadal later confirmed that his injury was tendinitis in his right knee, and will now also miss next month's tournaments in Beijing and Shanghai.
"I had to retire from the semi-finals of the U.S. Open and this past Monday I was with doctors in Barcelona to review the situation with my knee," Nadal wrote on Twitter.
"While my knee problems are nothing new, I have decided together with my medical and technical team not to participate in the Asian tour to recover."
Nadal tops the world rankings with 8,760 points. He is 1,860 points ahead of Federer and 2,315 ahead of in-form Djokovic.
Sixth seed Djokovic at the U.S. Open, beat Del Potro in the final to claim his second Grand Slam title this year and rise to third in the rankings, behind Nadal and Roger Federer.
With Federer cutting the number of tournaments he plays Djokovic is now favourite to unseat Nadal as world number one.
Federer only took part in events in Shanghai, Basel and the ATP finals after last year's U.S. Open.
(With Reuters Inputs)