Sloane Stephens, sidelined for 11 months by a left foot injury until returning in July, captured her first Grand Slam title by routing fellow American Madison Keys 6-3, 6-0 in Saturday's US Open final.
Stephens took a $3.7 million (3.07 million euros) top prize from the biggest victory of her career, pitted against one of her closest friends in the first all-US final since 2002 on the New York hardcourts.
With the 15th victory in her past 17 matches, Stephens became only the fifth unseeded player to win a women's Slam title, although Latvia's Jelena Ostapenko managed the feat at this year's French Open.
The only prior unseeded US Open women's champion was Kim Clijsters, who came back from retirement to take the 2009 title.
Stephens made only six unforced errors in the match to 30 for Keys, who had 18 winners to 10 for the champion.
It was the first final set of a US Open women's championship match where the loser didn't take a game since Chris Evert beat Evonne Goolagong 6-3, 6-0 in 1976.
Keys, seeded 15th, and 83rd-ranked Stephens each fought off injuries to reach the title showdown.
Stephens returned at Wimbledon and slid to 957th in world rankings before semi-final runs at US Open tuneups in Toronto and Cincinnati, while Keys underwent her second left wrist surgery after the French Open and won a tuneup title at Stanford.
Stephens will jump to 17th in Monday's world rankings while Keys, who took hom $1.825 million as runner-up, will rise to 12th.
In the firset set, Stephens broke to seize a 3-2 lead, Keys swatting a forehand beyond the baseline to surrender the game, and Stephens broke again when Keys send a backhand long to take the set after 30 minutes.
Keys made 17 unforced errors in the opening set to just two for Stephens, both in the last game.
In the second set, Stephens broke with a forehand crosscourt winner past on outstretched Keys to grab a 2-0 edge, then broke again on a double fault for a 4-0 lead, Keys swatting the ball with her left hand as it bounced back at her.
Keys forced triple break point in the fifth game but Stephens saved them all and held to 5-0.
The end came after 61 minutes on Stephens' third break and championship point when Keys netted a forehand.
Hands on hips, Stephens simply stood for a few seconds with a stunned expression, then smiled and made a tiny fist pump before going to the net to share a teary-eyed hug with Keys.
Neither Keys, 22, nor Stephens, 24, had ever reached a Slam final, only the seventh time in the Open Era (since 1967) two first-timers met for a women's Slam title.
But it was the second time in three years it happened at Arthur Ashe Stadium after Flavia Pennetta beat Roberta Vinci in 2015's all-Italian final.