Novak Djokovic stretched his winning streak to 15 straight at the ATP finals by beating Kei Nishikori 6-1, 6-1 Sunday.
The top-ranked Serb has not lost at the season-ending tournament at the O2 Arena since 2011. He has won three straight titles since then.
Before the match, the ATP held a minute's silence for the victims of the Paris attacks.
In the round robin group's late match, Roger Federer will face Tomas Berdych.
Nishikori beat Djokovic in the 2014 US Open semifinals, but the 25-year-old Japanese player has lost to the 10-time Grand Slam champion four times since then.
On Sunday, Djokovic lost only nine points on his serve and never faced a break point. With Nishikori serving, Djokovic won 30 of the 53 points.
Djokovic is having the best season of his career. He reached the final at all four Grand Slams, winning three of them. His only loss in a major this year came in the French Open final.
Besides his run at the ATP finals, Djokovic has won 38 straight matches indoors, a streak stretching back to 2012.