LONDON - Kei Nishikori produced a big upset against six-time ATP Finals champion Roger Federer, defeating the Swiss great in straight sets 7-6 (7-4), 6-3 in their first-round group match at the season-ending tournament on Sunday.
Nishikori, currently No. 9 in the world rankings, had not beaten the third-ranked Federer since 2014 and improved to 3-7 in head-to-head meetings against the 20-time Grand Slam champion with the win at O2 Arena.
“It was good that I took the first set tiebreak and converted the few chances I had in the second set,” said Nishikori, who has reached the semifinals of the ATP Finals twice.
“I don’t think of him as an unbeatable opponent. He wasn’t in his best form and it was a match I had to win. It means a lot to have won the way I did,” he said.
At one point, Nishikori hit a backhand so good it threw Federer off his game as he earned a code violation.
Two points away from losing the opening set and on the back foot in a rally, Nishikori hit a stunning shot up the line, which prompted Federer to hit the ball into the crowd and receive a warning for ball abuse.
“I thought ‘What was his argument, why the warning?’ ” Federer said of his exchange with the umpire. “But nothing more than that. He thought I was angry. I wasn’t. Now I’m angry because I lost, but I wasn’t, so. . .”
Federer earned the first break points in the opening game of the second set, and took his chance, but Nishikori hit straight back in the following game.
Nishikori was the far more composed player from that moment on and broke for a 4-2 lead before closing out the match.
“It’s always a big challenge to play Roger,” Nishikori said. “The first match is not easy.”
Federer, who has reached the semifinals in all but one of his 15 previous appearances at the tournament, will now likely need to win his remaining two round-robin matches to keep alive his chances of claiming the 100th title of his career.
More thanks to poor returning than good serving, neither man was able to create so much as a sniff of a break of serve in an error-strewn opening set, until Nishikori’s backhand denied Federer two set points with the score at 6-5, 15-30.
A tiebreaker followed and Federer made one of his 20 unforced errors in the set to give Nishikori the first mini-break and a 3-1 lead, which quickly became 6-1.
Federer rallied to save three set points, but Nishikori delivered a well-placed serve to ensure the comeback attempt ended there.
But his concentration deserted him moments later as a double fault gave Federer a break he did little to earn. But the Swiss responded in kind with a wild forehand error that leveled the score at 1-1.
“Unfortunately I couldn’t keep the lead that I got early (in the second set),” Federer said. “That was the key of the match, that sort of 10-minute swing at the end of the first through to maybe 1-1 in the second.”
The seventh-seeded Nishikori began to relax and was rewarded in the sixth game as he brought up another break point and produced an inside-out forehand Federer had no chance of returning.
Nishikori showed no nerves as he dropped just one point in his next two service games.
Earlier, Kevin Anderson made a confident start to his ATP Finals debut with a 6-3, 7-6 (12-10) victory over Dominic Thiem.
“I think it was important, you know, going out there and getting off to a good start,” Anderson said. “I definitely felt a little bit nervous.”