Roger Federer will surrender his world No. 1 ranking to Novak Djokovic after the 15-time major winner confirmed he is pulling out of the Paris Masters through injury.
Federer endured a painful defeat to Juan Martin Del Potro at the Swiss Indoors tournament in Basel on Sunday, a match that lasted a grueling two hours and 45 minutes.
And after his marathon match, he confirmed he would skip the Paris Masters in order to focus on the season-ending ATP World Tour Finals in London that start in early November.
That decision means he will lose the rankings points he accrued from three tournaments last year, and will be unable to overhaul Djokovic even if he wins his third straight World Tour Finals crown.
"It's just too much," Federer was quoted as saying on the official Paris Masters website after defeat in his home town.
"I was trying to make up my mind and I had some niggles I didn't want to take a chance on. I don't want to take a chance for London.
"I feel very disappointed as I had one of the best weeks of my life there last year, but this is just a last-minute decision."
Djokovic enjoyed a 53-week stay at the top of the rankings after his record-breaking 2011 until Federer regained top spot after taking his seventh Wimbledon title back in July.
But Djokovic will now end the year as world No. 1 for a second successive year, the first time that has happened since Federer held it between 2004 and 2007.
With Rafael Nadal out for the rest of the year with a knee injury, Andy Murray is the major threat to the dominance of Federer and Djokovic and the Briton says he is raring to go after missing the Basel tournament.