Kei Nishikori will be hoping to make another deep run at his most successful grand slam event after he outclassed Philipp Kohlschreiber 6-3 6-2 7-5 to reach the quarter-finals of the US Open on another scorchingly hot day in New York.

The Japanese 21st seed, a finalist at Flushing Meadows in 2014 and a semi-finalist in 2016, fired 29 winners to end the run of Kohlschreiber, who had beaten fourth seed Alexander Zverev in the previous round.

Nishikori appeared to be racing towards an easy win before Kohlschreiber unexpectedly broke the 28-year-old to level the third set at 5-5.

But that only delayed the inevitable as Nishikori kept his focus to seal the win and extend his perfect record against the German to 3-0.

“(I was) really lucky to finish in three sets — it was really hot on the court,” a sweat-soaked Nishikori said in an on-court interview. “I think we both struggled a little bit with the heat.”

Nishikori will next face either seventh seed Marin Cilic, which will be a rematch of the 2014 final, or Belgian 10th seed David Goffin.