NEW YORK, NY, USA - Canadian teenager Bianca Andreescu capped off her breakthrough 2019 season with Grand Slam glory at the US Open, playing indomitable tennis to survive 23-time Grand Slam champion Serena Williams, 6-3, 7-5 to win her first major title.

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Andreescu hasn't lost a completed match since February, and the Rogers Cup champion withstood a late hiccup to extend her winning streak to 13 straight and become the first Canadian woman to win a Grand Slam singles title in the Open Era, winning after one hour and 39 minutes on Arthur Ashe Stadium.

"I was feeling many, many things before the match, more than any other match," Andreescu said in her post-match press conference. "In the finals, playing Serena. I just tried to breathe as much as I could from the moment I woke up until the match. I tried to just do that throughout the whole match, to just keep my nerves in place.

"It wasn't easy at all. But I think that's what I've been doing really well throughout this whole year."

Williams, who broke Stefanie Graf's Open Era record of Grand Slam singles titles at the 2017 Australian Open, was making her fourth attempt to tie Margaret Court's all-time record of 24 after finishing runner-up at the last two Wimbledon Championships and 2018 US Open final.

Dropping just one set en route to the final, Williams, who spent 14 months away from the sport to marry and give birth to daughter Alexis Olympia, looked to begin with a strong service hold.

The BNP Paribas Open champion, undaunted in the face of the biggest match of her career, flipped a 40-15 deficit to break off a double fault from the American.

"I think there are some similarities. We like to keep the points short with our aggressive game style. We like to use our serve to our advantage. I think we fight really, really hard.

"But at the same time I want to make a name for myself. I know I have a different game style than many players on the tour right now. It's been working really, really well. It's been working to my advantage. I just want to keep improving it."

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The American initially remained within one break and aimed to pump herself up after saving a whopping five break points in the seventh game. Down break point on her own serve, the No.15 seed gamely saved it and broke once more in the next game to capture the opening set.

With a quick break to start the second, Andreescu shook off losing a long service game of her own to reclaim the initiative and race out to a 5-1 lead, holding her first championship point on serve. 

Williams saved it and put on a brave last stand, winning 16 of 20 points to level the set as nerves set in for the teenager. With her back against the wall, Andreescu stopped the run of games to again put herself within four points of victory. 

"I had some doubts because I've witnessed her come back from being 5-0 down, 5-1 down, 5-2 down," Andreescu said. "I just told myself to stick with my tactics. She started playing much better. I think the crowd really helped her, as well."

Striking a forehand winner for 15-30, Andreescu earned two more championship points when Williams ended a long rally with a backhand error. Saving a second match point off an ace, the American couldn't save a third as Andreescu batted a way a forehand winner to clinch victory.

"I told myself to put the goddamn ball inside the court and just breathe as much as I could because she was serving, first of all. I wanted to win the first point to show her that I am in it to win it."

In all, it was a clean match from Andreescu, who struck 18 winners to 17 unforced errors, converting five of 12 break point opportunities while winning a solid 64% of first serve points. 

Already set to make her Top 10 debut regardless of result, Andreescu is tentatively set to move up to No.5 on Monday's rankings.