NEW YORK, NY, USA -- Lesia Tsurenko of Ukraine moved into the first Grand Slam quarterfinal of her career at the 2018 US Open, outlasting 19-year-old Marketa Vondrousova of the Czech Republic, 6-7(3), 7-5, 6-2 in a lengthy, topsy-turvy affair on Monday.

Tsurenko, who ousted No.2 seed Caroline Wozniacki in the second round, physically struggled in the first set before engineering a remarkable comeback to oust the left-handed teenager in two hours and 32 minutes, and reach the final eight in New York after two previous fourth-round losses in Grand Slam events.

"I think it was some type of heat illness or something like that," Tsurenko told the media in her post-match press conference. "I have to say that I've never felt so bad on court. This was something new for me. I usually handle any kind of weather without any problem. But today was one of the toughest matches in my life."

"At the beginning of the second set, I could feel like a breeze, like a little wind, and it was cooler," Tsurenko continued. "Then I saw the shade, and I thought, 'Okay, I will try. I give myself some hope.' I think the good thing that I decide to keep fighting, and then I was feeling better and better, and I came back to the match."

The high-risk battle saw Vondrousova outpointing Tsurenko in winners by 25 to 17, but the Czech teenager also blasted 72 unforced errors during the encounter. Tsurenko was able to convert eight of 15 break points in the match, including three breaks of the Czech's serve in the decisive third set.

"I feel that I play more confident, I play more calm, and I feel that I have, like, a good spirit now," when asked about attaining her best major result at age 29. "I'm ready to fight. I'm ready for any kind of challenge on court."

In the quarterfinals, Tsurenko will face No.20 seed Naomi Osaka of Japan, who survived her own three-set tussle against No.26 seed Aryna Sabalenka of Belarus earlier on Monday.

"We played once, but many years ago, I think in some small tournament in Mexico, and she beat me," Tsurenko said of Osaka. "I was impressed with her serve and forehand. Nothing really changed in her game. She's just more consistent and even more powerful now. I think she likes to play on hard courts. She likes to attack all the time. I'm playing a little different style of tennis, so we'll see."

Tsurenko got off to a flying start, holding at love for 1-0, then reaching triple break point in the next game, and breaking Vondrousova with a forehand winner to take a 2-0 lead. But Tsurenko struggled with her movement as the set wore on, and Vondrousova drew back on serve at 4-3. Tsurenko fended off multiple break points to hold for 5-4, but received a visit from the trainer at the change of ends.

Vondrousova took a 6-5 lead by breaking Tsurenko and served for the set, but the Ukrainian saved a set point and broke for the tiebreak after Vondrousova pushed a forehand long. In the breaker, Vondrousova took the pivotal lead after Tsurenko fired an unforced error into the net for 5-3, and the Czech reeled off the final three points to lead by a set.

Vondrousova looked as if she was headed to a straight-set victory after quickly breaking Tsurenko for a 2-0 lead. But Tsurenko put the set back on serve after the next game, breaking back after busting a rally open with a deep forehand to force a netted error from the teenager.

Tsurenko continued to power her way beyond any lingering discomfort, and broke Vondrousova for a 5-4 lead. But, with Tsurenko serving for the set, Vondrousova directly broke back after a powerful crosscourt forehand forced a netted error from the Ukrainian.

But Vondrousova faltered on serve again, firing a number of unforced errors to drop serve again, and give Tsurenko a second chance to serve out the set at 6-5. Tsurenko would not let that opportunity slip away, closing out the second set on her first set point after a Vondrousova forehand flew long at the end of a rally.

Tsurenko raced through the opening stages of the decider, winning 12 of the first 13 points en route to a 3-0, double-break lead over the young Czech, who was now struggling with her own movement. But Vondrousova clawed back one of those breaks in the next game, halting the momentum of Tsurenko.

However, that was a minor stumbling block for the Ukrainian, who broke Vondrousova once more for a 4-1 lead, and rediscovered her crafty court coverage to serve for the match at 5-2. There, two match points went begging and Vondrousova held a break point, but the Czech squandered it with a long return, and Tsurenko eventually reached a third match point, with a backhand crosscourt winner, which she converted for the win.