Zheng shocks Swiatek in another incredible US Open comeback

"I would say I start the match really slow. That's why she's able to lead 5-0," Zheng said. "After that, I start to play more freely because I think I need to try to find my rhythm at least for the second set.

"I think that's the key for me to come back," she said. "I didn't expect that today, but somehow it's just happening again,"

As her rhythm built, Zheng said she was so in the moment that at one point she lost track of the score.

"At 4-5 I went to the towel, because I thought it was 3-5, and I thought I need to play one more game.

"But when I saw the scoreboard, I was, like, oh, 4-5, I need to go to my place to sit down.

"I was so focusing every single point, I just said, OK, this ball have to play here, that ball there, next point, just keep repeating," added Zheng, who saved three set points in the opening set.

Zheng was already the first qualifier to reach the US Open women's fourth round since Emma Raducanu -- who went on to win the title in 2021.

She will next face world number two Elena Rybakina, who cruised past two-time US Open winner Naomi Osaka 6-1, 6-4.

'Psychologically difficult'

Rybakina leads their head-to-head 4-1 and has won both meetings this year, in Doha and Madrid. She'll also have even more than a semi-final berth at stake since she's assured of climbing to world number one if she makes it to the final four.

Zheng, meanwhile, is fighting to get back to the top 10, admitting she's found it hard to accept her rankings plunge as she struggled to regain her form after her lengthy injury layoff.

"Psychologically it is very difficult to accept," she said. "I used to be top 10, Olympic champion.

"It is really, really tough process," Zheng added. "I suffered a lot, and I have been through a lot of pain every single loss I have."

Swiatek left the court in tears after another bitter Grand Slam disappointment.

She won her most recent major at Wimbledon last year but fell in the quarter-finals at the Australian Open in January before a fourth-round exit at Roland Garros and a third-round defeat in her Wimbledon title defense.

"I didn't have good timing," Swiatek said. "I wasn't hitting the ball right.

"Maybe I could have played more safe or something, but I also didn't feel like I had space with Qinwen to do that."