WUHAN, China -- Ukrainian teenager Dayana Yastremska notched a tremendous upset at the Dongfeng Motor Wuhan Open on Wednesday, stunning No.2 seed Karolina Pliskova of the Czech Republic, 6-1, 6-4, to book a spot in the quarterfinals in her tournament debut.

"I think I just did my job," Yastremska said during her post-match press conference. "I was really in a good courage today. I think I prepared myself well."

World No.27 Yastremska had earned five career wins over Top 20 players coming into her match with the Czech, but had yet to claim a Top 10 victory. That all changed with her thunderous 64-minute win over World No.2 Pliskova, which also avenged a tight three-set loss to the Czech in their only prior meeting, at Madrid earlier this year.

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"It's always nice to play against top players," Yastremska stated. "You always try to make everything as good as possible. So I enjoyed being on court. I didn't really put pressure on myself because I knew I had nothing to lose. I saw the screen. I'm [ranked] 28 and she is [ranked] 2. I was like, 'Okay.' I just tried to imagine I'm No.2, it was a bit easier."

19-year-old Yastremska fired six aces -- double that of the big-serving Pliskova -- and never dropped serve in the encounter, saving both of the break points she faced. The youngster fired 26 winners to just 15 unforced errors during her stellar display.

"I hope I can manage to stay now with the level I have and improve it and perfect my game," Yastremska continued. "We will see."

Pliskova, who leads the WTA in match-wins after her 50th victory of the year in the previous round, could only muster up eight winners during the tilt. The Czech's loss to Yastremska ends her chance to displace Ashleigh Barty as World No.1 at the end of the week.

Yastremska exhibited blistering form at the outset of the clash, cracking a forehand return winner to convert a break point in Pliskova’s first service game and earn a 2-0 lead. This hot start spurred the Ukrainian on to a massive run of form, as she held serve at love twice in a row to extend her lead to 4-1.

The teen was clicking on her forehand side in the first set, with most of her ten winners in the opening frame coming off of that side. Yastremska used that wing to queue up another break point at 4-1, and Pliskova handed over the break right there with an ill-timed double fault. Yastremska took her 5-1 lead and ran with it, sealing the one-set lead with an ace.

The second set was more competitive, but Yastremska was still able to garner the upper hand very quickly, blasting back-to-back return winners at the end of a lengthy game to break Pliskova for a 2-1 lead. The Czech had started to read the Yastremska serve more effectively at this point, powering sturdy returns with increasing frequency, but the Ukrainian survived another long game to consolidate the break and lead 3-1.

At 4-3, Pliskova finally earned her first break point of the match following a Yastremska double fault, but the teenager erased that chance with a serve-and-forehand one-two punch, then powered through three more deuces before holding for 5-3 with a backhand winner.

After a tough hold for 5-4, Pliskova grasped one last chance to break her opponent in that game. Once again, though, Yastremska summoned up her best when she needed it most, and fired an ace to swat that chance away. In the end, the early break held up for Yastremska, and after consecutive netted returns by Pliskova, the Ukrainian had notched a milestone victory.

In the elite eight, Yastremska will now face either No.5 seed Petra Kvitova of the Czech Republic or No.10 seed Sloane Stephens of the United States. Kvitova and Stephens face each other on Center Court following Yastremska’s victory.

"I will be happy to play with both of them," said Yastremska. "Again, I'm going to prepare myself. I'm going to look [at the] match. I'm going to make tactics. I'm going to go and play. But both of them are really tough players. They're a bit different. We will see. I mean, I'm happy to play with each of them. Another good experience."