NEW HAVEN, Conn. - Second-seeded defending champion Petra Kvitova of the Czech Republic beat seventh-seeded Agnieska Radwanska of Poland 7-5, 6-4 on Thurday night to reach the Connecticut Open semifinals.

"She's a smart player," Kvitova said. "She know where the ball will go probably before I know where it's going to be. She's a very good mover actually. I think that the serve is kind of the weakness of her game. I was trying to take advantage from it, to be aggressive from the first kind of shot."

Kvitova overcame a 5-3 deficit in the first set.

"Yeah, you know, I was trying," said Kvitova, who has been battling mononucleosis this summer. "When you are losing 5-3, you're just trying to do something probably a little bit different. I was really like risking too much, I think. I was really missing all those shots and I wasn't really in the good timing."

Kvitova advanced to the semifinals for the fourth straight year. She also won the event in 2012, then lost to Simona Halep in the 2013 finals.

Kvitova will play Denmark's Caroline Wozniacki on Friday. Wozniacki, the tournament champion from 2008-11, routed France's Caroline Garcia 6-3, 6-0 in the late match.

"It was nice to get it done in two sets," Wozniacki said. "Garcia is a young, good player and I knew she was going to go in and try to be aggressive from the start. But, I ran a lot of god balls down and managed to play pretty well."

Wozniacki is 5-4 against Kvitova, winning the most recent meeting last year in Singapore.

"It's going to be a tough one, I always have tough matches with her," Wozniacki said. "I'm just happy to be in the semis and take it from there."

Lucky-loser entry Lesia Tsurenko of the Ukraine beat fifth-seeded Karolina Pliskova of the Czech Republic 6-2, 6-2 in the first quarterfinal.

Tsurenko lost in qualifying, but got into the field when the top-seeded Halep withdrew because of an injury. Tsurenko has yet to lose a set in the tournament.

"I don't feel any pressure because I'm playing players who are higher ranked than me, so I have nothing to lose," Tsurenko said. "I can just beat them or lose to them. It just makes me happy to play in the main draw of big tournaments, for sure."

Tsurenko will face fourth-seeded Lucie Safarova of the Czech Republic. Safarova beat Slovakia's Dominika Cibulkova 6-7 (4-7), 6-4, 7-5 in a match that lasted 2 hours, 56 minutes.

"We had long points, some really fast rallies," Safarova said. "It was just about few points, but I'm really happy to get the win like that."

In Cibulkova's three tournament matches, she has logged just under nine hours on the court.

"It's been long matches, but that's what I came here to do — play matches," Cibulkvoa said. "I think this was the best of all matches I've played here."