Teenage sensation Biana Andreescu has continued her captivating 2019 season to gatecrash the US Open semi-finals in New York.

Ranked 178th in the world at the start of the year, Andreescu is through to her maiden grand slam final four after mounting a spirited comeback to beat Elise Mertens 3-6 6-2 6-3 on Tuesday night.

“I need someone to pinch me – is this real life?” the 19-year-old said.

The Canadian will play Belinda Bencic on Thursday night for a place in the finals after the Swiss backed up her stunning fourth-round elimination of world No.1 Naomi Osaka with a 7-6 (7-5) 6-3 quarter-final triumph over Donna Vekic earlier on Wednesday.

The 22-year-old’s own breakthrough is all the more satisfying after Bencic plummeted from seventh in the world to out of the top 300 in 2017 following wrist surgery.

“I was dreaming, of course, about this day coming, but you never know what’s going to happen,” she said.

“You’re not thinking about it. You’re just right in the moment. Either you’re practising or focusing on your match.

“I worked hard for this. It’s not like I never imagined I could do this. Still, like, I stayed in the moment. Yeah, very nice feeling.”

The 12th seed is Switzerland’s last hope in the singles following the quarter-final exits on Tuesday of men’s heavyweights Roger Federer and Stan Wawrinka.

“This is not a good thing. I’m not happy about this actually,” Bencic said.

“Yeah, I’m kind of surprised, like I think everyone is. It would be really nice if the boys could also make it to semi-finals. But I’m happy I can kind of do it for them and don’t let them down.”