Second-seeded Petra Kvitova beat third-seeded Caroline Wozniacki 7-5, 6-1 on Friday night to reach the Connecticut Open final for the fourth consecutive year.
The defending champion will play fourth-seeded Lucie Safarova in an all-Czech Republic final. Safarova held off lucky-loser Lesia Tsurenko of the Ukraine 6-2, 7-6 (7-4).
"We are friends and it's always difficult to play friends for sure, even in the final," said Kvitova, practices with Safarova during the Fed Cup and when back home. "It's not always easy, but that's how it is in tennis and when we are on the court I don't we are really thinking about the friendship."
Kvitova is 6-0 against Safarova.
"It's going to be a tough finals match, which it should be," Safarova said.
Kvitova also won the Connecticut tournament in 2012, and lost to Simona Halep in the 2013.
Wozniacki, from Denmark, won the last of her four New Haven titles in 2011.
Kvitova is fighting mononucleosis, and Wozniacki is slowed by leg and back woes.
Wozniacki was particularly sharp in building a 5-3 lead. However, Kvitova stormed back to take the next three games and go up 6-5.
In the tiebreaker, Wozniacki saved match point five times and the players went to deuce seven times before Kvitova prevailed. In the 12-game first set, the players went to deuce 19 times.
"Yeah, it was very similar to yesterday when I was 5-3 down, as well, and I had to really fight back," Kvitova said. "I think in the end of the first set, every game what we played was really close. It was just few points and could be on the other side.
"I was happy I won the first set. I was really happy because we play over the hour. So for me was good to be the first one, for sure."
Wozniacki won just one game in the second set, tying it at 1-1, before Kvitova began to dominate. In the last three games, Wozniacki managed just one point. Prior to the last game she had her left knee re-tapped, but said it wasn't a factor in the loss.
"She played very well," Wozniacki said. "She took the ball extremely early, went for her shots. I had my chances in the first set I didn't take. Then in the second set, I didn't play bad.
"She stepped it up a little bit, didn't really give me any free points. Then I started to try and force it a little bit too much and started making more errors."
Kvitova and Safarova last played in the quarterfinals at Wimbledon in 2014, but they practice together at the Fed Cup and also hit together when back home.
"I know her game a little bit, but on the other side she should know mine as well," Kvitova said. "I don't know I think in important moments I might be a little bit stronger player."
Safarova had a 4-1 lead in the second before Tsurenko rallied.
"I started to rush a little bit and I was not really concentrating in the moment," Safarova said. "She started pressing me and the whole momentum started to shift."
Safarova took a 5-4 lead, but Tsurenko, who replaced the top-seeded Halep in the field after losing in qualifying, staved off elimination and took a 6-5 lead.
In the double semifinals, Germany's Julia Goerges and the Czech Republic's Lucie Hradecka beat Americans Raquel Kops-Jones and Abigail Spears 1-6, 6-3, 10-2, and Taiwan's Chia-Jung Chuang and China's Chen Liang topped Germany's Anna-Lena Groenefeld and Sweden's Johanna Larsson 3-6, 6-3, 10-7.