Former world number one Roger Federer has suggested that British star Andy Murray's run of form is due to lack of competition from tennis's elite.

The top eight in men's tennis go head to head in the ATP World Tour Finals in London from this Sunday, with the British number one entering the tournament off the back of three wins in Bangkok, Tokyo and Shanghai.

"I'm not taking anything away from what Andy did, but was Asia the strongest this year?" The Telegraph quotes Federer as saying. "I'm not sure.

"Novak [Djokovic] wasn't there, I wasn't there and [in Shanghai] Rafa lost early.

"It has been a good effort by him after losing to Kevin Anderson in Montreal [in August]. Don't forget how things were looking then."

Despite Federer's apparent dig at the Scotsman, he does believe that the 24-year-old is on his way to claiming his first Grand Slam.

"I think he's past that tough hurdle - 'Oh, I haven't won a Grand Slam" - that stressed him out more one-and-a-half years ago," he added.

"I think now he is a bit more laid back because he has gone through these ups and downs and knows how to handle them."

The final competition of the season commences at the O2 in London on Sunday.