Zheng Qinwen won a set from 5-0 down for the second match in succession as she extended her fantastic US Open run by beating former champion Iga Swiatek to reach the quarter-finals.
Zheng, the reigning Olympic champion and former world number four, dropped outside the world's top 100 earlier this year while struggling to regain her best form following elbow surgery in July 2025.
The 23-year-old from China had trailed Madison Keys 5-0 in the deciding set of their third-round match on Saturday before winning seven successive games to secure her spot in round four.
And Zheng was 5-0 down in the opening set against Poland's eighth seed Swiatek, but won 13 of the next 16 games on Arthur Ashe Stadium to set up a quarter-final against second seed Elena Rybakina, who sped past former champion Naomi Osaka.
The second set was on serve until the seventh game, when Zheng crushed a powerful backhand return winner to secure a crucial break, and she broke again two games later to complete a 7-5 6-3 victory.
This latest win - her seventh in a row in New York having come through three rounds of qualifying - will put her back to the brink of the top 50.
"The more matches I play, the more rhythm I have on court," said Zheng.
"People have asked me if I'm tired and when I arrived I was not tired at all. I felt really pumped for my match, trying to reach better levels here and enjoy this fantastic stadium."
Elsewhere, French Open winner Mirra Andreeva recovered from losing the first set to Austria's Anastasia Potapova to reach the last eight in New York for the first time in her career.
For Swiatek, 25, a fourth-round exit is a disappointing end to her Grand Slam season, with a quarter-final appearance at the Australian Open her best result.
She was beaten in round four of the French Open, while the defence of her Wimbledon title ended in the third round.
It means that, for the first time since 2021, Swiatek will end a year without winning one of the sport's four majors.
Swiatek, who received treatment to her left thigh when leading 2-1 in the second set, had entered the US Open in excellent form by winning the WTA 1000 event in Toronto and getting to the semi-finals in Cincinnati, while she had progressed through to round four without dropping a set.
Reflecting on losing the first set to Zheng, Swiatek said she simply missed too many shots after going 5-0 up.
"My focus was the same as always," said the six-time major winner. "I wanted to play the same as always. [I] just started to miss too much, wanted to adjust it, but nothing kind of worked at that point.
"I knew I was going to have another chance and I wanted to use it, but I missed them all."
She continued: "I wouldn't say it had anything to do with mentality. It was more that I started making mistakes from easy balls and Qinwen stopped doing mistakes. She played the balls better."
