Kei Nishikori avenged his painful US Open loss to Stan Wawrinka as the Japanese star routed the world number three 6-2, 6-3 in his opening match at the ATP Tour Finals on Monday.

Nishikori was denied a second Grand Slam final appearance in September when Wawrinka defeated him in the US Open semifinals and the world number five got his own back with a dominant display at London's O2 Arena.

Despite being placed in a tricky Tour Finals group that also includes world number one Andy Murray, Nishikori hopes to make the final of the prestigious season-ending event for the first time after reaching the last four in 2014.

"I was very solid from the first game and very confident. It wasn't easy against Stan because he hits a lot of slice and a variety of shots, but I played a good game today," Nishikori said.