Tennis: Nishikori beats Federer in ATP Finals opener

LONDON. KAZINFORM Japan's Kei Nishikori produced a big upset against six-time champion Roger Federer, defeating the Swiss great in straight sets 7-6(4), 6-3 in a first-round group match at the ATP Finals on Sunday.

World No. 9 Nishikori had not beaten the third-ranked Federer since 2014 but he reduced his career head-to-head deficit with the 20-time Grand Slam champion to 3-7 with the win at the O2 in London, Kyodo reports.

"It was good that I took the first set tie-break 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.

In the 88-minute round-robin match, Nishikori took the tie break and the first set when Federer struck a forehand into the net. Federer made 20 of 34 unforced errors in the first set and got a code violation for ball abuse.

The 37-year-old Swiss, who is chasing his 100th singles title, hit the ball into the crowd in the 12th game in an emotional outburst and was warned by the umpire.

Meanwhile, Nishikori, 28, calmly capitalized on the few chances he had against his off-key opponent, breaking Federer's serve for a 4-2 advantage in the second set and serving out for victory.

Nishikori and Federer both play their second round-robin matches on Tuesday, with Nishikori playing South Africa's Kevin Anderson and Federer facing Austrian Dominic Thiem.

The Nov. 11-18 event, which features the top eight singles players and doubles teams in the ATP rankings, has a round-robin format. The top two in each group progress to the knockout semifinals.