ROGER FEDERER admits he misses his on-court battles with rival Rafa Nadal as the Spaniard continues his recovery from injury.

While Federer, Andy Murray and Novak Djokovic are starring at the ATP World Tour Finals in London this week, 2010 finalist Nadal is again absent from the big stage through a chronic knee problem.

Federer faces Janko Tipsarevic today but admits the competition is not as fierce with only three of the world's top four players in action at the 02 Arena.

He said: "Knowing that maybe the draw is potentially a little easier, there is no denying that because Rafa is a great champion.

"And I'm sure that he is missed by a lot of the fans, which would have made this tournament maybe even more exciting, but then it gives opportunities to one or two more guys.

"It's obviously never the same when Rafa doesn't enter a tournament, but from time to time injuries just do happen, and we all wish him the best so he can return next year."

He added: "I always knew Andy and Novak were going to stay around for a long time at the very top of the sport.

"So this is just right now it seems they are in their prime and this is when they are supposed to play their best tennis, in my opinion.

"Obviously we miss Rafa because he belongs in there, he won a grand slam this year.

"I would have loved to have seen him again and played him because I don't think I've played him in the last couple of years."