NEW YORK — At one moment, Novak Djokovic was bent over, grabbing his stomach. In another, he was pummeling the ground with his racket out of frustration. In many others, he stood slumped at the baseline, his arm trailing expectantly behind him, waiting for a ball person to deliver a towel into his hand.

Amid suffocating heat in Arthur Ashe Stadium on Tuesday, Djokovic was in a perilous state.

He had lost the second set and was down, 4-2, in the third to Marton Fucsovics, and with the oppressive conditions bearing down on him and everyone else in the building, Djokovic had only one thought about how to change his fortunes.

“I was actually praying that the next moment I could feel better,” he said. “I wasn’t feeling great for most of the three sets.”

But the sixth-seeded Djokovic won the last 10 games to defeat Fucsovics, 6-3, 3-6, 6-4, 6-0, in 2 hours 59 minutes under what was officially declared extreme heat by the U.S. Tennis Association.

Under a new extreme heat policy for men, the players were given a 10-minute break between the third and fourth sets. According to Djokovic, the combatants spent the time in the locker room, side by side, in ice baths.

“We were naked in the ice baths next to each other,” Djokovic said in an on-court interview. “It was quite a magnificent feeling, I must say.”

A first for Townsend

On Tuesday, 22-year-old Taylor Townsend claimed her first main-draw victory at the U.S. Open, defeating fellow American Amanda Anisimova, 3-6, 6-4, 6-3. Anisimova, who turns 17 on Friday, was playing her first main-draw match at the Open. She won the U.S. Open junior title last year.

Wozniacki stops drought

Caroline Wozniacki had not won a match since the first round of Wimbledon in July, and retired from her last match, in the second round at the Cincinnati event. Across the net from her Tuesday was another Grand Slam champion, Sam Stosur of Australia, who won the 2011 U.S. Open. Wozniacki rose to the moment with a crisp 6-3, 6-2 victory.