Novak Djokovic grinds into US Open third round after 'awful' serving display

Defending champion advances after Laslo Djere retires injured while Coco Gauff also progresses in the women's draw

Novak Djokovic battled past Laslo Djere, who retired early in the third set, to reach the US Open third round. Reuters

Novak Djokovic added another record with his latest win at the US Open on Wednesday night but admitted he needs to improve after an "awful" serving performance.

The four-time and defending champion led Laslo Djere 6-4, 6-4, 2-0 in their second-round match inside Arthur Ashe Stadium when his fellow Serb retired injured. It was Djokovic's 90th US Open match victory, becoming the first man to win 90 at all four Grand Slams.

While the scoreline might suggest a routine win, it was anything but for the second seed, who struggled on serve throughout, landing just 47 per cent of first serves, and he found himself 4-2 down in the second set.

"It's not what we want to see," Djokovic said of Djere's retirement. "He's such a good player in these conditions and the second set should have been his, he was 4-2 up. I don't know if winning the second set probably put more burden on him."

Djokovic, who underwent knee surgery in June, grabbed the first break of the match to take the first set 6-4 after a tense hour then sought treatment for trouble on his right side.

Djere, the only player to take a set off Djokovic at last year's US Open, gained the first break of the second set and with a 4-2 lead had two more break points that he couldn't convert.

But Djokovic won the next six games, Djere receiving treatment on his abdomen before Djokovic closed out the second.

"Overall it was a big fight – over two hours for two sets," Djokovic said. "I served awful. So playing without the serve, you have to grind, you have to run. I had to rely on my baseline game."

The Serbian superstar, coming off an emotional Paris Olympics triumph, next faces Australian Alexei Popyrin, whom he beat at the Australian Open and Wimbledon this year.

Gauff advances to third round

Women's defending champion Coco Gauff overcame her own struggles on serve to beat 37-year-old Tatjana Maria 6-4, 6-0.

It was an uneven performance from 20-year-old Gauff, who has endured an erratic season since capturing her maiden major in New York.

She put just 44 per cent of her first serves in play and had nine double faults, but the 99th-ranked Maria couldn't capitalise and Gauff won the last seven games to seal the win.

"I think I played well overall," Gauff said. "I think if I could have served better that first set would have been a lot easier."

Djokovic and Gauff missed the worst conditions of a steamy day that saw tournament organisers invoke the extreme weather rule allowing mid-match breaks.

Australian Open champion Aryna Sabalenka, runner-up to Gauff last year, didn't have to take advantage, polishing off Italian Lucia Bronzetti 6-3, 6-1 in an hour.

"I told myself you have to stay focused from the first point to the last point and make sure you're not going to stay here a crazy number of hours," Sabalenka said.

Fourth-seeded Alexander Zverev of Germany advanced with a 6-4, 7-6, 6-1 victory over France's Alexandre Muller.

"I am happy to be done in three sets, to have some rest as it is very hot and tough conditions," said Zverev, who said he felt fine but "was at some point very wet."

Zverev next faces Argentina's Tomas Etcheverry, whose efforts to stay hydrated backfired during his 6-3, 4-6, 6-4, 1-6, 6-3 victory over compatriot Francisco Cerundolo.

"You had to hydrate well, try to take as many salts and hydrates as possible and I overdid it, that's why I ended up vomiting," said Etcheverry, who fired 23 aces to finally seal the win after more than four hours. "It's dangerous not only for the players, but also for the public."

Sixth-seeded Russian Andrey Rublev and Czech Jiri Lehecka both battled through five sets to line up a third-round meeting.

Rublev, a four-time US Open quarter-finalist, beat France's Arthur Rinderknech 4-6, 5-7, 6-1, 6-2, 6-2 while Lehecka out-lasted American Mitchell Krueger 6-7, 0-6, 6-4, 6-4, 7-5.

Elsewhere, seventh-seeded Paris Olympics gold medallist Zheng Qinwen had to go the distance, rallying from a set down for the second straight match to beat Russian Erika Andreeva 6-7, 6-1, 6-2.

But eighth-seeded Wimbledon champion Barbora Krejcikova became the biggest upset victim of the women's tournament so far, bounced 6-4, 7-5 by Romanian qualifier Elena-Gabriela Ruse.