China's Olympic gold medalist Zheng Qinwen rallied from one set down to achieve a 4-6, 6-4, 6-2 win over Amanda Anisimova of the United States in the women's singles first round at the U.S. Open on Monday.

"It's a very difficult match for a first round. She's a tough opponent to face, but I'm glad at the end I found a way to be through the match and win this match," Zheng said.

"I had this experience already, so this time when I had success in the Olympic Games, to come to the next tournament, I say, everything starts at zero. You are not anymore the Olympic champion. Just be humble and try to work, fight every single match, because if you don't fight, you have a big chance to lose," she added.

China's Wang Yafan advanced to the second round after her opponent Maria Sakkari exited early due to an injury after the first set. However, the other two Chinese women's singles players on Monday faced first-round exits: Wang Xiyu lost to Diane Parry of France 7-6(2), 7-6(5), and Yuan Yue was defeated by Russia's Erika Andreeva 6-3, 7-6(7).

Defending women's champion Coco Gauff powered into the second round with a 6-2, 6-0 win over Varvara Gracheva from France.

"It is definitely a lot of pressure this tournament but I'm just enjoying it," said Gauff.

In the men's singles, China's 19-year-old Shang Juncheng earned his first U.S. Open win over Alexander Bublik of Kazakhstan, 6-4, 3-6, 5-7, 6-3, 6-4, in a match that lasted three hours and 34 minutes.

"Very happy and tired. Very tired. Interesting match against Alex. He has everything, he throws anything at you, some second-serve bombs, also drop shots, underarm serves, anything," Shang said.

"You really have to focus the whole match, and I'm glad I did all the way till the end. It was just a good win, and hopefully I can continue," Shang added.

Another Chinese player, Bu Yunchaokete, lost to Norway's Casper Ruud 7-6(2), 6-2, 6-2.

Defending champion Novak Djokovic eased into the second round with a straight-set victory over qualifier Radu Albot of Moldova, 6-2, 6-2, 6-4.

"It's always challenging to start, particularly when you haven't played on this surface for five, six months, and coming off an Olympic gold and playing on clay. I haven't had any official matches before the U.S. Open. So I'm expecting to be probably challenged a little bit more in the opening rounds. Hopefully, I can play better each day," the 37-year-old Serbian said.