Djokovic sweats his way into US Open quarter-finals

Novak Djokovic has appeared to struggle with the heat again at the US Open but defeated Joao Sousa to progress to a likely quarter-final with Roger Federer

Serbia's Novak Djokovic fires a return at Portugal's Jaoa Sousa in their round-of-16 clash at the US Open. Picture: Matthew Stockman/Getty

NOVAK Djokovic has sweated his way to a round-of-16 victory over Joao Sousa as the heat returns to the US Open, setting up a potential quarter-final meeting with Roger Federer.

Djokovic did his part in improving his perfect New York record in fourth-round contests to 11-0, leaving it to second-seeded Federer, who will take on Australian John Millman in the late contest on Arthur Ashe Stadium court, to give the fans what would be a hotly anticipated match-up.

A Federer v Djokovic clash would provide the perfect contest to propel the US Open into the second week, with the two champions having claimed seven titles at Flushing Meadows between them.

"The matches I've played against him (Federer) have shaped me into the player that I am today," said Djokovic, who beat the Swiss in the Cincinnati final in the lead-up to the final grand slam of the year

Unseeded Sousa, the first Portuguese player to reach the fourth round of any slam, never looked a threat to progress any further as his run came to an end in two hours.

The biggest concern for Djokovic might well have been the conditions as the heat returned after a few days of relief.

The 31-year-old Serbian sixth seed left the court at two sets and 2-1 up for a medical evaluation.

"I am not 21 anymore, that was 10 years ago. I still don't feel old, but at the same time there is a little biological clock that is not really working in your favour," Djokovic said.

"Heat was the adversity today. I've experienced that in the first round. It's tough."

The 13-time Grand Slam winner managed to convert five of six break-point opportunities to advance to the last eight.

Seventh-seeded Marin Cilic defeated David Goffin 7-6 (8-6) 6-2 6-4 to reach his fifth US Open quarter-final and set up a rematch of the 2014 final with Kei Nishikori, who outclassed Philipp Kohlschreiber 6-3 6-2 7-5.

After his late-night fightback to beat Australian teenager Alex De Minaur in the previous round, Cilic recovered from a break down in the first set but was otherwise in control of his two hour and 24 minute encounter against Belgian 10th seed Goffin.

Earlier, Japanese 21st seed Nishikori fired 29 winners to end the run of veteran Kohlschreiber, who had beaten fourth seed Alexander Zverev in the previous round.

"(I was) really lucky to finish in three sets, it was really hot on the court," Nishikori said in an on-court interview.

"I think we both struggled a little bit with the heat."

- Reuters