Novak Djokovic has admitted that he was "not even close" to his best form during last night's straight-sets defeat to Roger Federer at the ATP World Tour Finals.
Djokovic went down 7-5 6-2 in London to lose his 23-match winning streak and 38-match indoor winning run.
"You have those days when you are not feeling your best, not even close to the best," Djokovic told reporters. "Credit to Roger for mixing up the pace, giving me always a different ball. He used the slice and spin very wisely. He served very efficiently.
"I made a lot of, lot of unforced errors. I just handed him the win, especially in the second set.
"He tactically played well. Undoubtedly, he was the better player on the court. But I think I also allowed him to play and penetrate through the ball and dictate the tempo from the baseline."
When asked about Djokovic's claims that he "handed" Federer the win, the Swiss insisted that the world number one still needed to be put away.
"He handed [me] the win? Well, he wasn't as good as in the first set," Federer told reporters. "But I feel, honestly, with the way he's played this season, you still have to put him away.
"It's not an easy thing to do. It's not like he played terrible. I know he can play better. Why did he play that way? I'd like to give myself credit for that, quite honestly, yeah."
Federer's victory means that he is guaranteed a place in the semi-finals, while Djokovic will have to beat Tomas Berdych, who has already been knocked out, in his third match to ensure progress at the O2 Arena.
