From out of nowhere, Sloane Stephens is the U.S. Open women’s champion.

From a foot injury in August 2016, from surgery in January, from 16 weeks on crutches, from 957th in the world rankings just weeks ago, Stephens finds herself where she couldn’t have imagined.

With precision, persistence and performance, Stephens took apart one of her best friends, Madison Keys, 6-3, 6-0, on Arthur Ashe Stadium court Saturday, lifting the winner’s trophy not that long after it was all she could do to lift her leg.

It took her only an hour and a minute to win her first Grand Slam title in her first Grand Slam final. Her footwork was superb, her groundstrokes exacting, her serve good enough that Keys couldn’t make inroads. It was a complete-game shutout that left the Ashe crowd a little speechless, about as quiet as Stephens’ presence on the court.

With all the grunting and groaning that comes with the physical exertion, Stephens silently startles. No squawking of voice or even screeching of shoes. She arrives at the ball with the grace of a ballet dancer, releases a shot with an ease of effort, is consistently in place to play another and another and another.

Her stealth game is in contrast with an exuberant, effervescent personality off the court that was evident through the night sky at the Tennis Center.

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“Obviously, I could have — at the beginning of the tournament — I could have never said, ‘Oh, yeah, I think I’m going to win the U.S. Open,’ ” Stephens said. “That sounds ridiculous. At this point where I am and the comeback, it sounds crazy. When you said that the other day, ‘Oh, in four days you could be a Grand Slam champion,’ I was, like, really? Like, in four days? So it really puts things into perspective, I’d say.”

Stephens completely defused what had been Keys’ biggest weapon the whole tournament, her serve. Keys held serve with two aces in the opening game of the match. That was as easy as she would have it. Her serves kept coming back with the same regularity as her groundstrokes. She won only 20 of 40 first serves and six of 15 second serves. Forced to rally more than she had in her previous matches, her forehand blew a tire. She made 19 of her 30 unforced errors on the forehand. Stephens had a total of six unforced errors and not a single double fault.

“I made six unforced errors?” Stephens said. “Shut the front door!”

Stephens’ former coach, Paul Annacone, a former Long Islander, said this past week that the fight Stephens made to get back to the court after nearly 11 months out of the game has carried into her fight on the court. Her current coach, Kamau Murray, agrees.

“Absolutely. When she first came back, I told her this is not going to be fun. It’s going to be torture,” said Murray, who speaks nearly as quietly as Stephens plays. “But I said other athletes have done it twice. Don’t count the days until the next tournament. Just go day by day. Schedule things in the evening that you enjoy, because the next morning is going to be hell all over again.”

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Stephens’ fight, or the outward evidence of it, is something that has been called into question since she bloomed as a junior. Annacone believes that Stephens’ way of processing pressure is to internalize it. Murray doesn’t have any issue with Stephens’ fight because he never saw her play until he coached her in November 2015.

“You people are asking before this, before that — well, I never really watched her,” Murray said. “I had no preconceived notions. It was great to sort of start fresh. I had no negativity. I had no idea what to expect, and I think that helped our relationship.”

Keys had to start all over again this season after undergoing left wrist surgery in November and more surgery in June. There was nothing to tell her that this season would be anything but a battle to return to normalcy.

“I’m really disappointed,” she said. “But if you told me as I was getting on a plane to go have my second surgery that I could have a Grand Slam finalist trophy in my hands at the end of the year, I think I’d be really happy.”

When it was over, the two embraced at the net almost as long as the second set lasted. After Stephens, 24, visited the players’ box to hug her mom and coach and assorted others, she returned to sit beside Keys, 22, as they waited for the trophy ceremony, laughing and reeling with apparent joy.

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“Sloane has always had the talent,” Keys said. “I think not being on the tennis court for so long really helped her realize how much she loves the game, so in a lot of ways, I think it was the best thing that happened to her.”

Right now, second best. Best is Sloane Stephens, U.S. Open champion.