LEXINGTON, KY, USA - American teenager Cori "Coco" Gauff pulled off another impressive win on Wednesday at the inaugural Top Seed Open presented by Bluegrass Orthopaedics, upsetting No.2 seed Aryna Sabalenka, 7-6(4), 2-6, 6-4 to reach her first WTA quarterfinal of the year.

"I think my mentality pushed me to win," she said after the match. "We're both playing good tennis, and had our ups and downs in the match. At the end of the day, it came down to a couple close points."

Gauff shocked defending champion Naomi Osaka earlier this year at the Australian Open, and notched her second Top 20 win of the season over Sabalenka after two hours and 48 minutes on Center Court.

"It's pretty much impossible to play your best tennis for all three hours of a match. Keeping the level high throughout was pretty tough, but that's just tennis, playing in different conditions, and just starting back on tour. I'm not too upset with how I played; I'm most proud of how I handled myself, staying composed on the pressure points."

Playing her first tournament since Melbourne, the 16-year-old navigated through a tricky two-setter against fellow American Caroline Dolehide to book a first meeting with Sabalenka, who won her third career Premier 5 title at the Qatar Total Open before the WTA tour was suspended due to the COVID-19 pandemic.

2020 Lexington highlights: Gauff surges to Sabalenka upset

Sabalenka, who was pushed to three sets by Madison Brengle in her first round match, enjoyed the stronger start, pressing Gauff to four break points before nabbing the first break of the match. Gauff responded impeccably, flipping the deficit into a 5-2 lead, serving for the set one game later.

Undaunted, the Belarusian swung the momentum back her way as she reeled off four games in a row before Gauff forced a tie-break.

Gauff, who won her first WTA title last fall at the Upper Austria Ladies Linz, rolled out to a 5-0 lead in the ensuing Sudden Death, ultimately sealing the set with an impressive forehand putaway.

While Sabalenka trailed 2-5 in the first set, she found herself up by the same scoreline in the second, holding off a late surge from the unseeded American to even the match by breaking at love with a deep return.

The final set opened with multiple breaks of serve; Gauff twice led Sabalenka only for the No.2 seed to claw back even. 

Though Sabalenka dug out of another close game to put herself two games from victory, Gauff emerged from the changeover with the momentum, winning 12 of the next 14 points to serve out the nearly three-hour clash with a sleek forehand angle.

"Everything was an 'A' except for my serving. I definitely served better in my first match than today, but you're going to have good and bad days, and I like to go for my serves, so that's the give and take.

"I think my serve today was more mental than technical. Towards the end of the match, I started serving better, and I may have been overthinking at some points."

Standing between Gauff and a spot in the semifinals is rising Tunisian star Ons Jabeur, who opened play on Wednesday by surviving former World No.35 Olga Govortsova in three sets.

"I can always improve, and I always believe I can improve, but this was also only the second match. I thought I would be much more nervous coming into my matches, but I actually wasn't, and I just have this mentality to have fun and enjoy the competition. That's what I've been doing, and I would say it's better than I thought it would be, especially because last week, my practices weren't so good. This is definitely a big improvement from then."