Kei Nishikori suffered a straight-sets defeat at the hands of Roger Federer on Friday and was knocked out of the Paris Masters.
Nishikori, coming off a convincing win against South Africa's Kevin Anderson, lost 6-4, 6-4 to the world No. 3 in 1 hour, 19 minutes. He suffered his sixth straight loss against Federer, who improved to 7-2 against the 28-year-old Shimane native.
"Overall I made a lot of mistakes," Nishikori said. "It would have been good if I had been able to work a little more on my return game, but it didn't go like I had thought."
The loss ensures that Nishikori will remain ninth in the race to the eight-player ATP Finals in London, with Marin Cilic and Dominic Thiem, who occupy the seventh and eighth spots, having also advanced to at least the quarterfinals at the ATP World Tour Masters 1000 event.
Nishikori could still qualify, however, if either Rafael Nadal or Juan Martin del Potro, who both withdrew from Paris with injuries, pulled out of the season finale.
Currently 11th in the world, Nishikori is expected to return to the top 10 for the first time in over a year following a season-ending wrist injury sustained last August. He has reached the quarterfinals or better in his last six events.
Federer, a 20-time Grand Slam winner seeking his 100th career title, will face Serbia's world No. 2 Novak Djokovic in the semifinals.