NEW YORK — 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 (LIVE on TSN at 4pm et/1pm pt.) 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.

--

Watch Bianca Andreescu’s historic run with TSN Direct, the exclusive streaming service from TSN.

Live stream every match, must-see stories, highlights, analysis & more! Subscribe Now >

--

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.​