US Open: Djokovic advances to third round after Djere retires injured

New York: Defending US Open champion Novak Djokovic kept his bid for a record 25th Grand Slam title on track on Wednesday after fellow Serb Laslo Djere retired injured while trailing 6-4 6-4 2-0 in their second-round match.

Djokovic had needed five sets to get past Djere in the third round a year ago and it looked as though Arthur Ashe Stadium would see another epic clash between the two as Djere went up a break in the second set.

But the unseeded Serb appeared to pick up an injury midway through the set and Djokovic was gifted his 90th win at the US Open, making him the first man to reach that figure at each of the four Grand Slams.

"It's not what we want. It's not what the crowd wants, to see a walkover," Djokovic said.

"But he obviously had an injury that took him out of the Tour for some time and he is struggling to come back physically to this level. He's such a good player, especially in these conditions. It should've been his second set, honestly."

Four-times champion Djokovic, who had looked rusty in his opening round match, appeared to struggle in the sweltering conditions that tested competitors all day at Flushing Meadows, wrapping himself in ice towels on the changeovers.

Djokovic broke Djere to love in the 10th game of a tightly fought first set, benefiting from a series of unforced errors by his opponent.

The second seed had to work harder to hold serve in the opening game of the next set, fending off two break points, and then shouted in frustration as he let a break point opportunity slip through his fingers in the next game.

Djere looked to have the momentum as he broke his opponent in the third game of the second set and held serve in the next with a mighty ace.

But the evening fell apart for Djere when he winced after a serve in the eighth game and Djokovic converted a break point.

Djere, who missed part of the season after undergoing elbow surgery in April, appeared to struggle with his mobility from there and took a medical timeout after the ninth game, lying on the court as a physio massaged his abdomen and lower back.

Djokovic broke again in the 10th and Djere tried to fight on before retiring seven minutes into the third set.

Up next for Djokovic is Australian Alexei Popyrin, who took a set off him in their previous Grand Slam clashes at Wimbledon and the Australian Open this year.

"I'm happy to win four sets another time. Don't get me wrong. But he keeps on getting closer and closer, knocking on that door," Djokovic said.

"He's been playing some great tennis, so no reason for him not to believe that he can put up a great performance, and he's going to go for the win. I know that.

"But I know what to expect as well... I'm going to do my homework and see what needs to be done."