American Madison Keys left Naomi Osaka in tears after coming from behind to beat the 18-year-old and book her place in the US Open fourth round.
Osaka led 5-1 in the final set in Arthur Ashe Stadium but the 18-year-old crumbled under the pressure as Keys roared back to win the match 7-5 4-6 7-6 (7/3).
Keys described it as the best comeback of her career and the eighth seed goes through to meet Caroline Wozniacki in the last 16.
"I think just because this is the biggest stage that I have done it on," Keys said.
"I think I easily could have let a lot of emotions get in the way of being able to come back.
"Being able to kind of block out everything and just really fight through it and get back into the match, I was really proud of myself for that."
For Osaka, however, this was a painful defeat, particularly as she was on the cusp of reaching her first grand slam fourth round.
The Japanese, ranked 81st in the world, admits she grew tense when trying to close out the match.
"At 5-1 I was just very nervous," Osaka said. "I kind of wanted to close it out. I felt like I could rely on my serve at that point because I think she was serving at 5-1.
"It didn't really bother me that she held serve at that time but it really started freaking me out when she was going 5-2, 5-3, 5-4, those times."
Keys is considered a future major champion by many in the game and the 21-year-old will now play Wozniacki in her fifth consecutive major fourth round.
The pair have never met before at Tour level but Wozniacki has found form in New York, reaching the last 16 of a grand slam for only the second time since the start of 2015.
The Dane, a finalist here in 2009 and 2014, eased past Romania's Monica Niculescu 6-3 6-1.
"I have known Caroline for a while," Keys said. "She's done well here. She's going to be tough.
"I think she's playing well right now. It's always interesting once you get to the fourth round because everyone has won matches and they're feeling very confident."
Injuries and inconsistency have seen Wozniacki drop to 74th in the world rankings but the 26-year-old believes her time on the sidelines could also pay dividends at this stage in the year.
"I think I'm definitely more fresh than the other players probably at this point," Wozniacki said.
"I'm feeling good. I just want to take advantage of that and just play, have fun with it, and enjoy the rest of the year.
"No matter what happens, at this point I'm just going to take it as momentum going into next year."
Elsewhere, last year's runner-up Roberta Vinci also made it through to the fourth round, along with Britain's Johanna Konta and 14th seed Petra Kvitova.
In the last match of the day, second seed Angelique Kerber eased past American Catherine Bellis 6-1 6-1.
