NEW YORK – American Serena Williams’ name had just been announced as a winner at Arthur Ashe Stadium on Monday afternoon when Novak Djokovic, the No. 1 seed in the men’s draw, seemed to wake to the realization he was battling more than veteran Philipp Kohlschreiber.

Djokovic was making his first appearance in two years inside Louis Armstrong Stadium, a flatter, more intimate setting that, on this withering afternoon, sizzled like a baking tray. The place was packed with fans, but Armstrong could hardly offer the same sheltered atmosphere as the court below the multitiered stands at Ashe.

So there it sat, splayed like a piece of meat under a broiling heat. Temperatures rose into the upper 80s, and Djokovic came to understand this was not going to be a breezy fourth-round tuneup.

“I know that I definitely wanted to stay not too long out there,” said Djokovic, who won 6-1, 7-5, 6-4.

The heat certainly impacted No. 7 Eugenie Bouchard, a 20-year-old Canadian who played after Djokovic at Armstrong and required medical attention after falling behind 3-2 in the second set.

Trainers rushed to apply cold towels to her neck and rubbed ice packs along her thighs in an effort to lower her body temperature. At one point, Bouchard appeared too weak to snap open a sports drink handed to her.

After about a six-minute delay, Bouchard returned to the court and looked as if she might use the rest to her advantage. She broke Ekaterina Makarova’s serve to even the set at 4-4, but there was no comeback in the making.

Russian Makarova, the No. 17 seed, finished strong to advance to the Open quarterfinals for the second consecutive year with a 7-6 (7-2), 6-4 victory.

Bouchard said her vision had gone blurry, resulting not only from the heat but also several long and late matches she played during the first week.

“I don’t think I fully recovered from those,” she said.

The loss brought Bouchard’s breakthrough season at Grand Slam events to an end. She reached the Australian and French Open semifinals and was a finalist at Wimbledon.

Notes

• Williams beat Estonian Kaia Kanepi 6-3, 6-3.

• No. 3 Stan Wawrinka of Switzerland and No. 8 Andy Murray of Britain reached the quarterfinals before a marathon match between No. 10 Kei Nishikori of Japan and No. 5 Milos Raonic of Canada.

Nishikori beat Raonic 4-6, 7-6 (7-4), 6-7 (6-8), 7-5, 6-4 in 4 hours, 18 minutes.