Roger Federer concedes it will be tough to regain the mantle of the world's best tennis player, given the form of current No.1 Rafael Nadal.
Speaking ahead of the ATP World Tour Finals, which begin on Sunday at London's O2 Arena, Federer said Nadal would be hard to reel in, given he trails the Spaniard in the rankings by almost 4000 points.
"Sure it is challenging - it is going to be very difficult because Rafa is playing well," Federer said.
"It's not something I have in mind right now. The goal is to play well here in London and prepare for next season and hopefully at some stage get it back."
The reigning Australian Open champion has been drawn alongside David Ferrer, Andy Murray and Robin Soderling for the season-ending event - prompting Federer to declare his group the tougher of the two.
The other pool boasts Nadal, Novak Djokovic, Thomas Berdych and Andy Roddick.
"We're all playing well, unlike the other group which is a bit more up in the air, so it's two very different groups," the 29-year-old said.
Federer admitted he would be wary of the threat posed by Scotland's Andy Murray, who has enjoyed some recent success against the Swiss maestro.
"He's beat me the last two times we've played, so it shows it's a tough group," he said.
"I played him last year so I know what to expect from the crowd. They always really get behind Andy, but they are very respectful too so I enjoy it and I'm looking forward to playing."
The 16-time Grand Slam tournament winner will be targeting his fifth win in the ATP World Tour Finals, and if he is successful he will join Pete Sampras and Ivan Lendl as the only five-time winners of the event.