BRISBANE, Australia - American qualifier Jennifer Brady earned the biggest win of her career at the Brisbane International on Thursday, dispatching top seed and World No.1 Ashleigh Barty, 6-4, 7-6(4) to reach the quarterfinals.

"I'm very happy to get the win," she said during her on-court interview. "Ash is obviously a great player and a great person. It's a little bit surreal. I'm super stoked and I'm shaking a little bit, but I really played well today."

Brady was previously 0-7 against Top 10 players and hadn't taken a set from Barty in their two 2019 meetings; taking on the Aussie in front of her home crowd, Brady made use of her big serve and heavy spin to win in one hour and 31 minutes on Patrick Rafter Arena.

"The last two times I played her, she was pretty dominant. I think today, I knew what to expect and I was hoping not to lose three times in a row. She's obviously very solid and reads the game so well. I was fortunate enough to win a lot of free points on my serve and hold throughout the match."

Barty was playing her first singles match of 2020, having ended last year on top of the tour with a win at the Shiseido WTA Finals Shenzhen, which secured herself as WTA Year-End World No.1. Playing doubles with Kiki Bertens, the 23-year-old already won two matches before taking on Brady, who won three matches in qualifying before defeating former World No.1 Maria Sharapova in a thrilling third-set tie-break.

"Hopefully I'll be a main draw queen and won't be playing too many more qualifying tournaments!" she laughed. "It's always good to get a few matches under your belt before the main draw, and I'm really happy with all my matches so far. Hopefully I can keep going."

The American showed no signs of a letdown despite the late finish against Sharapova, scoring the lone break of the opening set and serving it out on her second opportunity.

Barty responded with the fighting spirit that has become her signature in what has been a breakthrough 12 months for the Aussie - winning her maiden major title at Roland Garros last spring - and twice edged to within a game of a deciding set.

"Jen was in control of the match," she said in her post-match press conference. "She was in the center of the court being the aggressor and I think you have to give credit where credit's due. Jen is, yes, she came through qualifying, but she's got ranking that's kind of well above, I think, what a lot of people give her credit for. And I hit with her earlier in the week and we had a great practice session. And yeah, she's made a few changes to her team as well and I think that's brought a better standard for her. She's playing some exceptional tennis, so I certainly can't take that away from her. She played a great match today and deserved to win.

"Of course I would love to go further. And I think, in my point of view, there's no more expectation from however many thousand people were out there today to when I play anywhere else around the world. I think I'm just trying to do the best that I can and obviously try and put my best foot forward and try and play my best tennis, because I know that they have obviously come to see quality tennis regardless of who is on the court. They have taken the time out of their day to come and watch some quality tennis. And I know that Jen and I played a quality match today, regardless of the result. And I think now I look forward to kind of doubles here and then maybe going to Adelaide."

Brady leveled both times and forced a tie-break, which she began with aplomb, racing ahead 3-0. Barty put down an impressive overhead to prevent triple match point, but Brady was undaunted, tracking a drop shot and forcing a missed backhand from the top seed.

Serving with two match points, the qualifier only needed one, blasting a powerful serve and bigger forehand to prompt one last error from Barty.

In all, she struck 15 winners to just seven unforced errors; Barty struck 25 winners but 16 unforced errors and couldn't engineer a break point on Brady's indomitable serve.

Standing between Brady and her first Premier semifinal is either two-time Wimbledon champion Petra Kvitova or fellow qualifier Liudmilla Samsonova.

2019 Toronto interview: Barty 'hungry to get better'