Switzerland's Roger Federer plays a return to to Japan's Kei Nishikori in their ATP World Tour Finals singles final tennis match at the O2 Arena in London, Sunday November 11, 2018. Image Credit: AP

London: All is well not well in the Roger Federer camp and the former world No. 1 is the first person to admit it.

Minutes after losing in straight sets against Japan’s Kei Nishikori, the 37-year-old felt that he will have to make a marked improvement in his game if he is to remain in the fray for a 100th career title.

Scheduled to play Austrian youngster Dominic Thiem in his second round-robin match on Tuesday, Federer admitted that he will have to perform at a much better level. “We haven’t played in a while, I don’t remember when that was the last time. I mean, okay, whatever. I haven’t thought about the match to be honest [against Thiem]. I haven’t had enough time. I wasn’t even thinking who I’m going to play next,” Federer told media at the post-match after crashing 6-7 (4), 3-6 to Nishikori late on Sunday.

“I just know I need to do better than today. That’s pretty much it,” he added.

Nishikori became to the first player to ever beat Federer in straight sets in a round-robin match at the ATP Finals. This stat is made even more startling with the fact that Federer has competed at the event for 16 consecutive years starting in 2002.

The current world No. 3 admitted he struggled to get out of the blocks quickly. He was far from his best while making 20 unforced errors in the opening set which allowed Nishikori the chance to win the tiebreaker. “Well, I felt we both struggled throughout the first set,” Federer said.

The drama didn’t stop there as the Swiss star was handed a code violation by umpire Damian Steiner for sending the ball into the 17,000-strong crowd that had turned up to watch the late match. Federer’s face turned ashen and he struggled to get out of second gear as Nishikori broke twice — one more than the Swiss — to take the second set.

“I want to do well at every tournament. I think fans know that. Tournament directors know that, I know it and my team knows it,” Federer later explained.

“I think I’ve had that pressure of not going out early most of my career. Once I became world No. 1 anyway. Once you’ve been a former world No. 1, you always have that for the rest of your career, for every guy. I knew that my season was never going to be exactly like last year. I knew that going into the season,” he added.

“I’m happy with how I played this season. I didn’t feel like playing less was a problem,” he added.