NEW YORK -- Bianca Andreescu became the first teenager to reach the US Open semifinals in a decade, beating Elise Mertens 3-6, 6-2, 6-3 Wednesday.
The No. 15 seed dropped a set for the first time in the tournament, but recovered to improve to 31-4 this season, during which she's won two titles.
The 19-year-old Canadian became the youngest semifinalist at Flushing Meadows since Caroline Wozniacki was also 19 when she was runner-up in 2009.
Andreescu is also two wins from becoming Canada's first Grand Slam singles champion.
"If it happens, then I think I can pave way for many other athletes, the next generation,'' she said, "not only for Canadian tennis, but I think for many people.''
Basketball Hall of Famer Steve Nash tweeted about her. So did WNBA player Kia Nurse.
"It's really cool having other Canadian athletes shout me out like that,'' Andreescu said. "I think it gives me extra motivation to just keep striving and keep doing well.''
The 25th-seeded Mertens was bidding for her second major semifinal, having lost in that round at the Australian Open in 2018.
Andreescu will now face Belinda Bencic, who wore down Donna Vekic and advanced to her first Grand Slam semifinal with a 7-6 (5), 6-3 victory.
Six-time US Open champion Serena Williams faces fifth-seeded Elina Svitolina in Thursday's other semifinal.
Coming off her upset of top-ranked Naomi Osaka in the fourth round, 13th-seeded Bencic kept up her big hitting and broke open a close match midway through the second set by winning eight consecutive points.
She had been trailing 3-2 in the set, but that run sent her into the lead, and Vekic never recovered, with Bencic winning the final four games to surpass her 2014 run to the US Open quarterfinals for her best performance in a major tournament.
"I just really like the challenge," she said of playing in big matches. "I think some players are a little bit afraid of the big courts, but for me it's more motivation."
Belinda Bencic beats Donna Vekic 7-6, 6-3 to advance to the semifinals of the US Open.
Vekic, seeded 23rd, was also seeking her first semifinal in a major tournament. But with her face bright red as the sun beat down on Arthur Ashe Stadium, she couldn't keep up with her friend's power during the biggest moments of the match.
"I think she was just playing better tennis overall today," Vekic said. "I felt like I couldn't get three good points together. I was, like, playing one point good, then bad."
It was Bencic who cracked first, missing an easy putaway on game point while serving at 4-all in the first set. She momentarily seemed to lose focus, as Vekic then won the next three points to break for a 5-4 lead.
But Bencic broke right back to even it again and eventually they headed to a tiebreaker, where 22-year-old Bencic has thrived this season. Trailing 2-1, she ran off five of the next six points before eventually wrapping it up to improve to 10-2 in tiebreakers this season.
Vekic recovered to take a 3-2 lead in the second set, but that 10-point fifth game seemed to take a little out of her, with Bencic running off the next eight points to seize the lead.
Bencic, who has dealt with injuries since her lone quarterfinal here five years ago, has worked in the past with fellow Switzerland native Martina Hingis. She is coached by her father, Ivan, whom she acknowledged during her postmatch interview.
"I think he almost died today as well by heart attack," she said.
The Associated Press contributed to this report.