"This is, honestly, so insane", she said on court after the match.

"It would be really nice if the boys could also make it to semifinals", she said, "but I'm happy I can kind of do it for them and don't let them down". The 19-year-old 15th seed has been dominating the courts of the USTA Billie Jean King National Tennis Center and is now set to face the 13th seed, Belinda Bencic, in the semifinals on Thursday night under lights of Arthur Ashe Stadium.

"This is honestly so insane", the 15th-seeded Andreescu said after tour-high 29th win on hard courts this year. "The passion's always there, though".

"If someone had told me I'd be in the semifinal of the U.S. Open a year ago, I'd say you're insane". The then 18-year-old qualifier beat top seed Caroline Wozniacki, Venus Williams, and Hsieh Su-wei before losing the final to Julia Goerges. "I kept that passion going". The 19-year-old's breakthrough season includes her first career WTA titles at Indian Wells and Toronto. In between, she battled a shoulder injury that forced the Canadian to retire in the Round of 16 in Miami and the second round of the French Open. She also lost in the Wimbledon finals to Simona Halep.

She becomes the third Canadian woman to reach the final four in Flushing Meadows and the first since 1984.

Minutes later, with one last backhand down-the-line victor, Bianca Andreescu was a US Open semi-finalist.

You don't often see a teenager and Grand Slam debutant as the favorite for the title but Bianca Andreescu has been precisely that at this year's US Open, arriving in NY as one of the players to beat after claiming the title in Toronto.

After a rough start, Andreescu managed to muster up all the strength that she had to pull off one of the biggest victories in Canadian tennis history.

Andreescu has flipped that normal pattern on its head in her rookie season, beating seeded players and former Grand Slam champions with shocking regularity.

Belinda Bencic knew there was sadness in Switzerland after Roger Federer and Stan Wawrinka departed the U.S. Open on the same day.

Sporting News has the scoring and highlights from the Andresscu-Mertens quarterfinals match below.

She would then serve out the match. Andreescu now up to 10 winners and eight unforced errors.

In the quarterfinals, Mair called all four winners correctly. The teen has a 7-0 record against the WTA's Top 10 this year and her win-loss record for 2019 is the highest winning percentage of anyone on tour.

Serena Williams is halfway to a return to the U.S. Open final after winning the first set 6-3 over Elina Svitolina. Andreescu still held serve in the game, but it was an example of the type of shots Mertens was hitting. Their on-court conversation quickly went viral, as Andreescu tried to console a crying Williams. She also benefited from Anett Kontaveit withdrawing from the tournament in the third round ahead of their matchup.

During the tournament to get this stage, however, Bencic does have a marginal edge on numbers (6.4% edge on service points won, 5.0% deficit on return points won) so Andreescu's progress to a final is far from a foregone conclusion, so the stage is set for a very competitive match. It is go time.