NEW YORK, NY, USA -- No.6 seed Petra Kvitova of the Czech Republic overcame a spirited challenge from Kateryna Kozlova of Ukraine on Wednesday, eventually notching a 7-6(3), 6-2 victory to book her spot in the third round of the US Open.

Two-time Wimbledon champion Kvitova was challenged by World No.99 Kozlova in their first meeting, and the Czech was forced to save a set point at 5-4 in the lengthy opening frame before steering her way to the one-hour and 40-minute straight-set triumph on Arthur Ashe Stadium.

"In the first set, it was kind of tough," Kvitova said, during her post-match press conference. "I was really fighting a little bit the opponent, but with myself as well. There was a lot of nerves over there. I lost my serve and I was still down, and I still tried to come back and answer."

"When I won the tiebreak in the first set, it's been a little bit easier," the Czech continued. "I was more relaxed, more, kind of, calmer. That really helped me. Beginning of the second set I got the break, and it was a little bit easier for me to -- I was breathing a little bit more free."

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The US Open is the only Grand Slam event where Kvitova is yet to reach the semifinals, but the former World No.2 was still able to clinch a gutsy victory with 33 winners to 22 unforced errors. The first serve, as expected, was key to Kvitova's victory, as she won 89 percent of points on the day when that shot successfully found the service box.

Kozlova used some pristine passes and stunning groundstrokes on the line to keep the match competitive, as she sought the third Top 20 win of her career. However, the Ukrainian was still unable to post a milestone third-round showing at a Grand Slam event, falling to 0-4 in second-round matches at majors.

The vaunted Kvitova serve took a while to warm up, as the Czech had five double faults in her first three service games. That eventually proved to be costly for the seeded player, as the fifth of those put her down an early break at 3-2. Kozlova used impeccable passing shots throughout to flummox Kvitova, and continued to hold her lead up to 5-4.

Serving for the set in that game, Kozlova fell behind 0-40, but key aggressive play by the Ukrainian pulled her back to deuce, and a long return by Kvitova followed, queuing up set point for the underdog. But a fierce forehand by the Czech erased that chance, and finally, on her fifth break point of the game, Kvitova got level at 5-5 after a netted forehand by Kozlova.

Kvitova perked up, and it became her turn to garner a set point at 6-5, but a brave Kozlova pounded groundstrokes on the lines during the ensuing rally, eventually rocketing a backhand up the line to pull back to deuce. Kozlova gritted out the hold, lining up a tiebreak to settle the tense set.

Kvitova double faulted to open the breaker, but that proved to be a rare misstep as the two-time Wimbledon champion’s serve and forehand appeared in full force when she needed them most. A fierce forehand by the Czech extracted an error to give Kvitova four more set points at 6-2. On her second, another forehand winner thundered through the court, and the 67-minute set went to the seed.

Rejuvenated by the first-set comeback, Kvitova started the second set with a bang, thumping a huge backhand return to set up a forehand winner on break point and taking an immediate 1-0 lead. Two routine service holds followed, and the Czech was zooming ahead at 3-1.

After another superb passing winner, Kozlova was a point away from holding for 3-2, but a winning volley by Kvitova pulled the game to deuce. The sixth seed then garnered three break points in that game; Kozlova courageously saved two, but on the third, a net-clipping volley by Kvitova was just barely too much for the Ukrainian, and the Czech earned a second break for 4-1.

Serving for the match at 5-2, Kvitova slammed a backhand winner to reach triple match point. She only needed one, as a strong serve was returned wide by Kozlova, and Kvitova moved into the US Open third round for the tenth time in her career.

World No.12 Kvitova will face another tough opponent in the third round: either American Jessica Pegula, who reached the Western & Southern Open quarterfinals last week, or Kristen Flipkens, who knocked the Czech out of 2013 Wimbledon.

"I don't really know [Pegula's] game, so it will be more about to watch her a little bit, for sure, and, you know, talk a little bit with my coach," said Kvitova.

"With Kirsten, of course, we played a few times," Kvitova continued. "I know her game. She's very tricky, a lot of slice, a lot of dropshots. She has a variety of her game, really. She's still a dangerous player...I have to be patient if I'm playing with her."

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