Coco Gauff poses with the trophy after defeating Aryna Sabalenka to...

Coco Gauff poses with the trophy after defeating Aryna Sabalenka to win her first Grand Slam title in the U.S. Open women’s singles final at Arthur Ashe Stadium at the USTA Billie Jean King National Tennis Center on Saturday. Credit: Newsday/J. Conrad Williams Jr.

There’s a question people ask when a young athlete ascends to a sport’s grandest stage: Can she be as good as imagined, as good as promised? Can reality meet expectation when the expectations are so impossibly high?

For one set Saturday afternoon, there was doubt.

Coco Gauff, long heralded as the future of the women’s game, was off-kilter and, for the first time this U.S. Open, the American teenager looked her age. Second-seeded Aryna Sabalenka dominated with power and maturity, and it felt as if Gauff, in only the second Grand Slam final of her career, had strapped on some wings and flown too close to the sun.

Little did everyone know, Gauff was made of fire.

In a stirring, gritty, astonishingly athletic display, Gauff came back to take the final two sets, defeating Sabalenka, 2-6, 6-3, 6-2, to capture the women’s final at Arthur Ashe Stadium and win her first career Grand Slam title.

At 19, she is the youngest American woman to win it since Serena Williams took home the title in 1999 at 17. It’s only the second time in 29 U.S. Open women’s finals that a player has lost the first set and come back to prevail. She’s won 18 of her last 19 matches.

“Thank you to the people who didn’t believe in me,” she said on court. “To those who thought you were putting water on my fire, you were putting gas on it. I’m burning so bright right now.”

Then again, during her post-match news conference: “I’m very stubborn . . . So I really told myself, literally up until, like, 10 minutes before the match, I was just reading comments of people saying I wasn’t going to win today.”

So she simply did the opposite.

Gauff’s game seemed to mature and refine as the match went on, and the adoring crowd did its best to propel her when things looked bleak.

Gauff dropped the last three games of the first set, Sabalenka’s set point coming off Gauff’s unforced error on the forehand side.

Gauff refused to let the moment become too big for her, though, and relied on steely defense to unsettle Sabalenka. Gauff won the first four games of the third set, often outmaneuvering her opponent, eventually sealing it after Sabalenka committed three unforced errors on the way to love-40 in the final game.

Then, finally, came a running backhanded passing shot down the baseline that Sabalenka couldn’t handle for the win. Gauff collapsed to the court weeping as chaos erupted at Ashe.

“In the first set I was dealing with my emotions quite good,” Sabalenka said. “I was focused on myself, not on the crowd or the way she moves . . . But then the second set I started probably overthinking, and because of that, I started losing my power.”

Sabalenka committed 46 unforced errors, 27 on the forehand, and Gauff won five of nine break points.

Sabalenka’s consolation? On Monday, she’ll be ranked No. 1 in the world.

“Today was the first time I’ve ever seen my dad cry. He doesn’t want me to tell you that,” said Gauff, who immediately ran into the stands to hug her parents.

She talked about the pressure she felt when she burst onto the stage at 15, and how it sometimes sapped the joy of living the dream. Losing at Wimbledon in the first round in June, she said, dimmed it more.

That’s over.

“I just realize that I just need to go out there and try my best,” Gauff said. “I remember I lost when I was 17 and there was a stat, they were like, ‘Oh, she’s not going to win a Slam before Serena’s age.’ It was stuff like that that I felt like I had a time limit on when I should win one, and if I won one after a certain age, it wouldn’t be an achievement.”

Gauff said that as the trophy sat on the table in front of her. She may be older than Williams was when she won her first, but their names will be etched together all the same.

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