After winning his third tournament in a row at the ATP World Tour Finals to end the season ranked No. 3, Roger Federer, who did not win a major this year, says that he had to pick himself up mentally in order to have such a strong run in the fall. Federer lost to Novak Djokovic in the semis of the Australian Open, Rafael Nadal in the final of Roland Garros, Jo-Wilfried Tsonga in the quarterfinals of Wimbledon, and to Djokovic again in the U.S. Open semifinals.

"I think it's a mental thing, yes," he told reporters. “Not only. Sometimes it's also the player playing better than you. Jo played better than me at Wimbledon. Maybe not much, but enough just to come through. Same as Rafa (Nadal) at the French Open in the final, Novak in the semis of the U.S. Open. It's fine to respect that. But I feel when it happens that often, I do have to question myself that maybe I did something wrong. I think I'm mentally good right now. That was also one of the reasons why I did take some time off, to actually think it through, get into the right mental mindset. There is a lot of time that goes by out on tour, during a match, you're just trying to stay positive, but you can't always be positive out there. It's just too difficult. That's where maybe the doubts were just a bit too strong during certain important moments. I wanted to get that out of my system during the six-week break, and I was able to do that."

Federer added that his U.S. Open loss to Djokovic—where he held two match points against the Serbian for the second consecutive year—really stung.

"It was one that hurt," he said. "It was one that makes you wonder, 'How in the world can I end up losing this match?' But Novak had such great momentum going this season, you just felt like it was his season. But to bounce back and not lose a match from that moment on I think shows, again, how tough I am, the right decisions I can take."