NEW YORK -- The second set was slipping away from Coco Gauff in the US Open's fourth round Sunday, so maybe she was frustrated by that ... or the stumble that left her doing the splits while getting broken ... or the pair of double faults that helped Caroline Wozniacki take that game.

Or perhaps it was simply that the last thing she wanted to hear at that moment was the near-constant chatter coming from Brad Gilbert, one of her two coaches sitting in the front row at Arthur Ashe Stadium.

Either way, Gauff turned toward Gilbert and said, "Please stop." Then, during the next game, which allowed Wozniacki to force a third set, Gauff told him, "Stop talking."

That was while Wozniacki was in the midst of grabbing four consecutive games and going up a break early in the third set. And then, just as the match seemed to be slipping away thanks in part to a slew of unforced errors, Gauff straightened out her strokes and pulled away. She collected the last six games for a 6-3, 3-6, 6-1 victory over Wozniacki, the 33-year-old mother of two who recently came out of retirement.

During her on-court interview, the sixth-seeded Gauff described the interaction with her entourage as a "stress reaction."

"I was getting frustrated. It wasn't really directed at him. It was just that I needed to reset," the sixth-seeded Gauff said. "In that moment, I just didn't want to hear anything. I just wanted to think about what I was doing."

It turned out to be a good call. With the victory, Gauff became the first American teenager since Serena Williams more than two decades ago to reach the quarterfinals at Flushing Meadows in consecutive years.

In 2022, Gauff lost to Caroline Garcia in that round; this time, the opponent will be No. 20 seed Jelena Ostapenko, who defeated top seed Iga Swiatek, 3-6, 6-3, 6-1 in the fourth round.

Gauff, whose best showing at a major was reaching the final at the 2022 French Open, has now won 15 of her past 16 matches. That run follows a first-round exit at Wimbledon in July and includes the two biggest titles of her career, at the DC Open and in Cincinnati. It also coincides with the additions of Pere Riba as her full-time coach and Gilbert in a role that has been described as a temporary consultant.

TV microphones have been picking up Gilbert repeatedly offering his thoughts to Gauff during matches over the past week.

Against Wozniacki, the 2018 Australian Open champion and twice the runner-up in New York, Gauff was trying to find the right balance between being the aggressor (what she wanted) and not going for too much (what Gilbert wanted).

Gilbert's "scouting reports are quite accurate," Gauff said. "Sometimes you have to change things up. Today I had to change things up."

It was the hottest day of the event so far, with the temperature reaching 90 degrees Fahrenheit (32 Celsius), and Gauff kept missing the mark in the second set, to the tune of 22 unforced errors. But she cleaned that up considerably down the stretch, with just eight miscues in the last set.

"She's always been a great athlete," Wozniacki said. "She's always had the backhand, the serve, the fighting spirit. I feel like right now, it's all kind of coming together for her."

In the third set, with the playing surface covered in shadows, Wozniacki told chair umpire Louise Azemar Engzell it was difficult to see the ball and requested that the stadium lights be turned on.

"I would really appreciate it," Wozniacki said.

Didn't happen. And Wozniacki, the 2018 Australian Open champion and twice a runner-up in New York, was not able to match Gauff stroke-for-stroke down the stretch.

"She's back and it's like she never left," said Gauff, who has won three of her four matches in the tournament in three sets. "To be out here on the court with her today was an honor."

Another women's quarterfinal matchup will be No. 10 Karolina Muchova against No. 30 Sorana Cirstea.

Muchova, a finalist at Wimbledon in July, reached the US Open quarterfinals for the first time by beating Wang Xinyu 6-3, 5-7, 6-1. Cirstea hadn't been to the final eight at any major since the 2009 French Open and got back to that round by defeating No. 15 Belinda Bencic 6-3, 6-3.

The Associated Press contributed to this story.