Vera Zvonareva of Russia won the first four games of the third set, then held on for a 5-7, 6-4, 6-4 win over fifth-seeded Ana Ivanovic of Serbia in the semifinals of the Mercury Insurance Open on Saturday night.

The top-seeded and third-ranked Zvonareva, who won a hardcourt event last week in Azerbaijan, will play Agnieszka Radwanska of Poland in the finals. Radwanska beat Andrea Petkovic of Germany, 4-6, 6-0, 6-4, in the other semifinal.

"At the end, I came up with the good shots when I needed to," Zvonareva said.

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Zvonareva raised her game substantially as she won the first four games of the third set after losing a tough first set, then needing seven set points to finish off the second.

But trailing 5-1 in the third, Ivanovic came back to win three straight games and force Zvonareva to serve for the match. The Russian, who had a match point on her serve at 5-3, finally closed the match when Ivanovic netted a forehand.

"I started to play more aggressive," Zvonareva said. "I felt like sometimes I was going for some crazy shots and making some wrong decisions. But I knew that I had to push myself to keep trying them. They didn't work in the first set, then they started slowing working and it helped me to win the match."

Zvonareva, the two-time Grand Slam finalist, reached her third final this season and increased her winning streak to a career-high nine matches. She forced a third set after squandering six set points before finally hitting a backhand winner to nail down the second set.

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The Russian broke Ivanovic's serve in the first game of the match. The pair then held serve until Ivanovic broke back in the 10th game to even the set at five-all. After Ivanovic held serve, she won the set when Zvonareva double faulted on set point.

Radwanska, seemingly still bothered by a right shoulder injury, rebounded from losing the first set by winning 10 straight games to win the second set and jump ahead 4-0 in the third.

Petkovic revealed she was sick to her stomach when she took the court, and that it got worse as the match wore on. Petkovic eventually sprinted off the court during the second set to go to the bathroom so she could vomit.

"Is it more embarrassing running off the court like a maniac or throwing up on court and being on SportsCenter for the next 25 years?" Petkovic asked. "Yeah, running off the court is better, so that's what I did."

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Radwanska took advantage of the situation and raised her game while Petkovic dealt with her issue.

"I think I was more relaxed," Radwanska said about losing the first set. "I just thought I have really nothing to lose. She's playing well, this is the semifinal. I was really starting to play much better, playing aggressive, pretty much no mistakes."

Radwanska reached her first championship match since she lost here last year to Russia's Svetlana Kuznetsova. She will be seeking for her first title since 2008 and her fifth overall.

Petkovic, who took advantage of Radwanska's weak serving, looked to be in control after the first set. The right-handed hitting Radwanska has had a nerve issue in her right shoulder since last week at Stanford. The injury affects her most on her serve. She routinely hit first serves in the mid- to low-80s (m.p.h.) with her second serves in the 70s.

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Radwanska broke Petkovic's serve in the first game of the second set and took complete control of the match.

With Radwanska holding at 4-0 lead in the second set and Petkovic serving at 0-40, Petkovic sprinted into the stands and off the court. Petkovic had advised tournament supervisor Melanie Tabb and chair umpire Kerrilyn Cramer during the changeover at 3-0 that she needed to go to the bathroom because she felt sick to her stomach.

But she was advised that since Radwanska was serving the next game, it would be considered a time violation if she left. Petkovic waited until her serve in the fifth game before she hurriedly left the court.

"I think I ate something wrong for lunch," she said. "After the first set, I felt drained and I felt like vomiting all the time."

The delay didn't help as Radwanska finished off the set and continued her strong play into the third set when she broke Petkovic twice.

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"I felt much, much better (after vomiting)," Petkovic said. "The problem was I dropped intensity after the little incident."

Petkovic then regained her stroke from the first set as she ran off three straight games to get back in the match. After both players held serve, Radwanska finally ended the rollercoaster match on her first match point when Petkovic netted a forehand.

"Obviously, she was starting to play incredible in the third set," Radwanska said. "I didn't really change anything. She was just playing unbelievable."

Radwanska lost 6-0 in the first set of Friday's quarter-finals against Daniela Hantuchova before coming back for a three-set win.

Petkovic, currently ranked 11th, is projected to reach No. 10 for the first top-10 ranking of her career. She also will become the first German in the top 10 since Anke Huber in October 2000.