Serena Williams has called Bianca Andreescu an "old soul."

Others have called the 19-year-old Canadian "a boss" on the court.

And Andreescu is just getting started.

After her second match victory at her first-ever U.S. Open, Andreescu was asked in a post-match interview if anyone scares her at this point.

"If I just go out there and play my game, I think I can beat anyone right now," she said without hesitation.

She's got the swagger of a champion. The confidence of a player who has won Slams before. And yet this is all new to Andreescu.

Watch Andreescu's three-set victory that propelled her to the quarter-finals:

The 19-year-old Canadian battled past American Taylor Townsend 6-1, 4-6, 6-2 under the lights at Arthur Ashe Stadium. 1:51

You'd never know it.

The Mississauga, Ont., native has taken the tennis world by storm this year. And now she's preparing to take to the court on Wednesday night for the biggest match of her career.

As the stakes get higher and the pressure intensifies, Andreescu keeps rising. She is 16-3 in three-set matches this year, including 11 straight wins. Outside of time missed due to injury, she's been nearly unbeatable this season, posting a 42-4 record.

Now she's preparing to play in her first-ever Grand Slam quarter-final match inside the tennis coliseum that is Arthur Ashe Stadium — the largest tennis venue in the world. It's the third time during this year's U.S. Open that Andreescu is playing at Ashe.

Memorable moments during meteoric rise

If she was supposed to be shaken and fazed by the big stage, she's hasn't been. Keep in mind that this is Andreescu's first appearance at the U.S. Open; last year she lost in qualifying for the tournament.

But what a difference a year makes.

Andreescu defeated American qualifier Taylor Townsend 6-1, 4-6, 6-2 on Monday night in front of a rowdy and sometimes rude New York crowd to advance to a final-eight meeting Wednesday with No. 25 seed Elise Mertens of Belgium.

Andreescu, right, offers a hug to Taylor Townsend following the Canadian's win on Monday in the fourth round of the U.S. Open. (AFP/Getty Images)

"I heard some Canadian fans here and there, which was nice, especially in tougher moments," Andreescu said after Monday's win. "It's not easy. I tried not to pay attention to that, but it's hard when it's, like, everyone. I'm glad with how I managed to just keep my cool."

Andreescu has provided some memorable moments on the court in her short time in the spotlight, including a historic win at Indian Wells in March.

But perhaps the moment that endeared Andreescu to Canadian sports fans most was her emotional encounter with Serena Williams last month in the Rogers Cup final in Toronto.

"I'm sorry I couldn't do it today," Williams said, crying after retiring from the match just four points in. "Bianca, you're a great sportsperson, woman."

Watch Andreescu console Williams after the tennis icon retired from the Rogers Cup final:

Bianca Andreescu and Serena Williams shared an emotional embrace after Williams was forced to retire from the Rogers Cup final due to injury. Andreescu is the first Canadian woman to win the Rogers Cup since Faye Urban in 1969. 2:14

Andreescu then took the microphone at centre court to soak up her championship moment — once again showing poise and grace in the big moment, beginning with acknowledging her competitor.

"Serena you made me cry. I know how hard it is to pull out of a tournament due to injury. It's not easy," Andreescu began. "This isn't the way I expected to win. You are truly a champion. I've watched you play so many times. You are truly a champion."

It was this moment that won Williams over. In her post-match interview she called Andreescu an "old soul" for her grace in that moment.

It sent Andreescu's stardom into greater orbit.

'Just the beginning'

There's an authentic exuberance and joy that exudes from Andreescu whenever she's in front of the microphone. She seems to be soaking up every one of these moments right now.

And while she's shown her ability to act mature beyond her years on the court, finding the right words at the right time and the right shots under pressure, there are still moments that remind spectators of her youth — like on Saturday, when she was told she had cracked the top 10 of the Women's Tennis Association rankings.

"I don't usually check these things, I like to just focus on my game," she said, trying to hold back a surprised laughter.

"Wow, that's all I can say right now."

The most wholesome😍<a href="https://twitter.com/Bandreescu_?ref_src=twsrc%5Etfw">@Bandreescu_</a>'s reaction to hearing she's cracked the top 10 rankings is everything you need this weekend.<a href="https://t.co/ub6M1H183u">https://t.co/ub6M1H183u</a> <a href="https://t.co/wLVahW9zWi">pic.twitter.com/wLVahW9zWi</a> —@cbcsports

Andreescu's success this season has only been matched by her self-confidence. Now, with a top 10 spot in the rankings secured, she has an opportunity for another major moment under one of the brightest spotlights in tennis.

"This is just the beginning," she said after her Rogers Cup win.

Canadian sports fans are certainly eager for what comes next.