NEW YORK, NY, USA - No.15 seed Bianca Andreescu booked her first Grand Slam quarterfinal in some style, surviving a second set hiccup to defeat American qualifier Taylor Townsend, 6-1, 4-6, 6-2 in the early morning hours to become the first Canadian woman since Patricia Hy-Boulais to reach a US Open quarterfinal at the US Open.

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Starting the match late on Labor Day, the reigning Rogers Cup and BNP Paribas Open champion extended her hardcourt winning streak to 10 in a row - and won her 16th three-setter of the season - as Monday ticked into Tuesday, winning after one hour and 55 minutes on Arthur Ashe Stadium.

"I tried to just make her play as much as possible because, in the second set, I felt like she was doing that to me, I was missing more," said Andreescu. "I just told myself to be more aggressive but also patient at the same time."

The first set began with a flurry of winners from Andreescu, who matched Townsend for net approaches in the opening two games to secure a first break of serve.

Crunching a backhand down the line to earn a 4-0 lead, the No.15 seed found herself briefly pegged back only to win the final two games to take the set in 31 minutes behind an impressive display of offense.

Townsend, who rallied from a set down to defeat Wimbledon champion Simona Halep, began the second set in fine form, showing marked improvement on her serve placement to get on the board early and take a 3-0 lead.

Making her US Open main draw debut, Andreescu responded in kind to level the set and earn a break point for a fourth straight game, which Townsend saved with an audacious approach to the net.

The qualifier's serve started to click from there, holding twice more to move within a game of a deciding set. Playing steady tennis from the baseline, Townsend struck a forehand up the line to engineer a set point on Andreescu's serve, which she took off a seventh double fault from the Canadian.

Andreescu enjoyed a stronger start to the decider, breaking in the opening game and saving a break point on her own serve with a swing volley winner en route to consolidating. 

Townsend was keeping things close but two loose points on serve opened the door to a double break from the BNP Paribas Open champion, who constructed some high-quality points to move within two games of victory.

On the brink of defeat, Townsend saved four match points on serve - the third with a gutsy forehand passing shot - to force the Canadian to take it on her own serve. Undaunted, Andreescu surged out to another 40-0 lead, taking it on her fifth match point.

"She doesn't give you any rhythm whatsoever," said Andreescu. "She'll hit a flat ball, then a slice, she'll come to the net. In those moments I just tried to keep up with her, make sure to put pressure right from the start of the point with my serve, with my return.

"I think I did that pretty well in the first and third set. That's why I was winning the points. After the second set, that's what I told myself, just to make sure I put my first serve in the court because I knew she was going to attack my second serve."

Standing between Andreescu and her first Grand Slam semifinal is Qatar Total Open champion and No.25 seed Elise Mertens, who ended the run of American wildcard Kristie Ahn in straight sets earlier in the day.

"It feels awesome," added Andreescu. "I've been working and dreaming of this moment for a really long time, so it feels pretty damn good to be in the quarters here.

"I am really happy, but the tournament's not done yet. I think I can do even better than get to the quarters here this year.

"Every tournament I go into, I want to win it. I expect a lot from myself. But I'm going to just take it match after match because I know I have a lot of tough opponents before I reach the final. This year has been the best year of my life so far. I've never felt this confident before."