Olympic champion Zheng Qinwen fought back from a set down to beat world number 50 Amanda Anisimova 4-6 6-4 6-2 on Louis Armstrong Stadium.

Anisimova raced out to a 5-1 first-set lead but twice failed to serve out the first set, before breaking Zheng for the third time to close it out.

But Zheng, a little over three weeks on from her Olympic triumph in Paris, recovered well and served superbly from then on to secure victory.

The Chinese seventh seed said it was the “typical match” she would have lost in the past, adding that victory was “one step forward in my mental side”.

“Usually after huge success I will get a little bit too high, and until the reality slap me down again and I come back to the ground,” Zheng said.

“So this time when I get a success, I’m telling myself, I don’t want to let this happen. I’m really happy to get this match, because she’s really tough to face.”

Daria Kasatkina, the 12th seed, beat Romania’s Jaqueline Cristian 6-2 6-4 to progress, while Ukrainian 27th seed Elina Svitolina came through in three sets against Maria Lourdes Carle of Argentina.

However, Maria Sakkari became the first top-10 player to fall, with the ninth seed forced to retire injured after losing the first set to Wang Yafan.

A visibly upset Sakkari received treatment from the trainer to her shoulder and neck midway through the first set, and was ultimately unable to continue into a second.

American 14th seed Madison Keys, runner-up at Flushing Meadows in 2017, moved past Katerina Siniakova of the Czech Republic 6-4 6-1.