Roger Federer’s ATP Finals tilt takes a big hit after straight sets loss

“I’m glad to win, it’s never easy to play with my idol,” Nishikori said.

“I lost to him twice in the last two months so I played more aggressively and things started working, especially in the second set.

“There were some lucky points but I played well today.”

Federer made an uncharacteristic 36 unforced errors, 20 in the first set, and cut a disgruntled figure at times – even given a warning for swiping a ball high into the stands.

He admitted his practice has been “a bit all over the place” but had no excuses.

“I felt we both struggled throughout the first set. You could tell it was sort of a first round,” he said.

“I had my chances maybe a bit more than he did. Then I started to feel better in the second set. I think we both did. The level went up but unfortunately I couldn’t keep the lead that I got early.”

Federer does, of course, still have the chance to progress in the tournament with Austrian Dominic Thiem his next opponent.

However, he will be wary of a big obstacle in his group in the shape of Kevin Anderson, the 6ft 8in South African who knocked him out at Wimbledon this year.

Anderson, making his first appearance at the ATP Finals at the age of 32, looked determined to make up for lost time as he beat Thiem 6-3 7-6 (12-10).

“I definitely felt a little bit nervous,” Anderson said.

“But I was able to settle very quickly and find a really good rhythm, taking care of my serve games nicely, created quite a few opportunities on his serve.”

Thiem simply could not make any inroads on the Anderson serve and admitted he lost to a potential title challenger.

“He’s very dangerous. He serves well. I think out of the taller guys, he’s playing outstanding from the baseline. Of course, he can win the title here,” he said.

World No.1 and tournament favourite Novak Djokovic will face American tournament debutant John Isner in his group opener while Alexander Zverev and Marin Cilic face off in Monday’s other match.

AAP