New York (AFP) - Novak Djokovic will aim for a fast start against fellow Serbian Laslo Djere on Wednesday as he steps up his bid for a record 25th Grand Slam singles title at the US Open.

Djere, ranked 109th in the world, was the only player to take a set off Djokovic at last year’s US Open, taking the first two of their third-round clash before Djokovic turned the tide on the way to a 24th major crown, which tied him with Margaret Court for most all-time.

Djokovic, coming off an emotional triumph at the Paris Olympics, will anchor a night session that opens with women’s defending champion Coco Gauff, 20, taking on 37-year-old Tatjana Maria of Germany.

While 37-year-old Djokovic quipped he could do with an earlier bedtime, both he and Gauff could be grateful to miss the worst heat of a steamy day that saw tournament organizers invoke the extreme weather rule and grant mid-match breaks to distressed players.

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.

The world number two from Belarus, aiming to become the first woman since Angelique Kerber in 2016 to win both hard court Grand Slam titles in the same year, said she was determined to make it a quick to avoid the worst effects of the heat.

“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, applauding the decision to partially close the Louis Armstrong Stadium roof to provide some shade.

Seventh-seeded Paris Olympics gold medallist Zheng Qinwen had to go the distance, rallying from a set down for the second straight match to reach the third round with a 6-7 (3-7), 6-1, 6-2 victory over Russian Erika Andreeva.

China’s Zheng next faces German Jule Niemeier, a 6-4, 6-0 winner over Moyuka Uchijima of Japan.

“Honestly today, my entry to the match wasn’t the way I wanted, but I’m glad I still fought until the end and didn’t give up,” Zheng said.

Having bagged China’s first Olympic tennis singles gold, Zheng is now aiming to follow compatriot Li Na as a Grand Slam winner after coming up short against Sabalenka in the Australian Open final.

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

- Amazing tennis -

In men’s action, fourth-seeded Alexander Zverev of Germany advanced on cue with a 6-4, 7-6 (⁷⁄₅), 6-1 victory over France’s Alexandre Muller.

“I thought he played some amazing tennis. Especially at the end of the second set, I thought he was the better player than me,” Zverev said. “I am happy to be done in three sets, to have some rest as it is very hot and tough conditions.”

Zverev next faces Argentina’s Tomas Etcheverry, who appeared to be feeling the heat when he vomited on court during his 6-3, 4-6, 6-4, 1-6, 6-3 victory over compatriot Francisco Cerundolo.

Etcheverry fired 23 aces to finally seal the win after more than four hours.

“The conditions were very difficult, honestly,” Etcheverry said. “We were expecting them, but the temperature was 38 degrees and to that we have to add another four degrees inside the court.

“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.

“It’s dangerous not only for the players, but also for the public,” he added.

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 (⁵⁄₇), 0-6, 6-4, 6-4, 7-5.

Ukrainian Marta Kostyuk had little energy to celebrate her 7-6 (¹²⁄₁₀), 6-1 victory over Britain’s Harriet Dart, making her way to her courtside chair and re-applying ice packs to her head and neck.