NEW YORK (AP) It was way back in March, before Bianca Andreescu had ever won a WTA title, when she lost in the semifinals of a tournament in Acapulco, Mexico.
That's the last time the Canadian finished a match on the wrong side.
Six months and two titles later, that's the way 15th-seeded Andreescu rolls into the U.S. Open final against Serena Williams on Saturday with a chance to win her first Grand Slam title.
''Hopefully I can just keep the momentum going for the finals,'' Andreescu said.
The 19-year-old is 33-4 this season after beating No. 13 Belinda Bencic 7-6 (3), 7-5 in Thursday's semifinals. She's the first Canadian in a Grand Slam final since Genie Bouchard at Wimbledon in 2014, and the first teenager to play for the U.S. Open title since Caroline Wozniacki did it a decade ago.
Andreescu followed her semifinal loss to Sofia Kenin in Mexico on March 1 by making her first title a good one, becoming the first wild card to win at Indian Wells later that month. She then went to Miami and had to stop playing in her fourth-round match with a right shoulder injury - officially her last loss.
That kept her sidelined until the French Open in May, when Andreescu won her first match and then had to withdraw before her second-round match, again because of the shoulder.
That forced her to miss Wimbledon and the entire grass-court season before coming back last month in Toronto, where she won the title when Williams had to retire in the final because of back spasms.
Andreescu seemed headed to a third set Thursday when she fell behind 5-2 in the second set. But she didn't drop another game from there, saying she believes her best tennis comes out when she's down.
''I think it's just inside of me somehow,'' Andreescu said. ''I think it's just my passion for the game as well. I don't like to lose.''
She almost never does.
Ash Barty is a win away from a second straight U.S. Open women's doubles title.
Barty and Victoria Azarenka routed Viktoria Kuzmova and Aliaksandra Sasnovich 6-0, 6-1 in a semifinal match that lasted just 56 minutes.
Barty won the women's doubles title last year at Flushing Meadows with CoCo Vandeweghe. Vandeweghe was still recovering from ankle problems this year so Barty is teaming with Azarenka, who like Barty is a former top-ranked singles player and major champion.
Barty will return to No. 1 in singles after the U.S. Open.
Barty and Azarenka, the No. 8 seeds who beat American teenagers Coco Gauff and Caty McNally in the third round, will face wither the fourth-seeded team of Elise Mertens and Aryna Sabalenka, or Caroline Dolehide and Vania King of the U.S.
Wimbledon champions and No. 1 seeds Juan Sebastian Cabal and Robert Farah have advanced to the U.S. Open men's doubles final.
They will face No. 8 seeds Marcel Granollers and Horacio Zeballos for the title.
Cabal and Farah advanced by beating Jamie Murray and Neal Skupski 7-6 (5), 7-6 (8) in Thursday's semifinals.
Cabal and Farah are the first men's doubles pairing from Colombia to win a Grand Slam trophy and to be ranked No. 1.
Granollers and Zeballos also won a two-tiebreaker semifinal, defeating Kevin Krawietz and Andreas Mies 7-6 (2), 7-6 (5).
None of the four finalists ever has won a U.S. Open men's doubles title.
Cabal and Farah were eliminated in the semifinals a year ago.
Granollers was a runner-up in 2014 and a semifinalist two other times with different partners. Zeballos was a semifinalist in 2010.
The way Naomi Osaka consoled Coco Gauff after beating the 15-year-old American in the U.S. Open's third round was admired by many. On Thursday, Osaka was given the women's 2019 U.S. Open Sportsmanship Award.
Diego Schwartzman was the men's honoree.
Both get a trophy and a $5,000 donation to a charity of their choice.
Todd Martin, the former player who is co-chair of the committee that chooses the recipients, said the two ''demonstrated a level of sportsmanship that is even more impressive than their play on the court.''
AP Tennis Writer Howard Fendrich contributed to this report.
More AP tennis: https://apnews.com/apf-Tennis and https://twitter.com/AP-Sports