Canadian teenager Bianca Andreescu is eagerly awaiting Saturday's US Open title showdown with 23-time Grand Slam champion Serena Williams, in a rematch of last month's Toronto final that was cut short by injury.

The 19-year-old Andreescu, playing at just her fourth Grand Slam and making her US Open main draw debut, has enjoyed a rapid rise over the past nine months after finishing 2018 ranked 178th in the world.

She became just the second Canadian woman — after Eugenie Bouchard at Wimbledon in 2014 — to reach a Grand Slam final following Thursday's 7-6 (7/3), 7-5 win over Swiss 13th seed Belinda Bencic.

Andreescu will on Saturday face a record-chasing Williams, who won her first major title at the 1999 US Open before Andreescu was even born.

The pair recently met at the Rogers Cup in Toronto, but it was a brief encounter, with Williams retiring while trailing 3-1 in the final due to a back injury.

"I've wanted to play her. I remember always telling my team I would have always wanted to play her right before she retires. I'm really looking forward to it. She's an amazing champion on and off the court. It's going to be fun," Andreescu said.

"A lot of emotions are running through my body right now. A lot of thoughts, too. But right now I'm just trying to take in the victory of tonight.

"Hopefully I can just keep the momentum going for the finals. Hopefully I can play a little bit better than I did today."

Andreescu is the second teenage Grand Slam finalist this year — after French Open runner-up Marketa Vondrousova — and will bid to become the first teen Grand Slam champion since Maria Sharapova won at Flushing Meadows in 2006.

Back against the wall

"If someone told me a year ago I would be in the US Open final this year, I'd tell them they were crazy," Andreescu said.

"I don't think I would have believed them. I was ranked, like, outside of the 150, I think. It's just crazy what a year can do. If someone would have said that a couple weeks ago, I think I would have believed them."

Andreescu saved a set point in the opening set against fellow first-time Grand Slam semi-finalist Bencic before edging the tie-break.

She then trailed by a double break at 5-2 in the second set but reeled off the final five games to close out the match.

"I think when I'm down, I play my best tennis. Whenever my back is against the wall, I think I'm just extra focused in those moments," Andreescu said.

"I remember I told myself at 5-2 that I didn't want to go in three sets. So I think just that switched my mindset. I was just really, really focused."

Andreescu owned just two Grand Slam main draw victories coming into this Flushing Meadows fortnight, and had fallen in the first round of US Open qualifying the past two years.

"I wasn't going through a good period in my life at that point," she said, asked for her memories of a first-round loss to Olga Danilovic in 2018 qualifying.

"I was having problems with some relationships in my life, with my body, and even my mind, too. I was playing 25Ks, I remember, 60Ks in Canada before the quallies of the US Open.

"But I'm glad I went through it because at one point you have to. I think I just learned a lot."