DUBAI, United Arab Emirates -- Former Wimbledon champion Petra Kvitova overpowered defending champion Agnieszka Radwanska 6-2, 6-4 to set up a semifinal against former No. 1 Caroline Wozniacki in the Dubai Championships on Thursday.
Wozniacki needed more than two and a half hours to get past Marion Bartoli of France, whose aggressive play was undermined by 14 double faults -- two that cost her games in the second set -- and 46 unforced errors.
Doubles specialist Roberta Vinci of Italy surprised former U.S. Open champ Sam Stosur 6-2, 6-4 in their quarterfinal and will face doubles partner Sara Errani after the seventh-ranked Italian overcame 12th-ranked Nadia Petrova of Russia 6-4, 0-6, 6-3.
No. 4-ranked Radwanska had no answers for the big-hitting Kvitova, who neutralized the Pole with a powerful forehand that contributed to 37 winners.
Neither player managed to hold serve in the nervy first five games. But then eighth-ranked Kvitova held for the first time to go up 4-2 and broke for a fourth time to make it 5-2. The second was tighter but Kvitova took control when she converted a fifth break chance in the game to go up 4-2. The Czech won the match with a powerful forehand that Radwanska returned weakly into the net.
"I think to beat Agnieszka here it means something more because she's defending champion, so she's playing well here," said Kvitova, who has a 4-1 record against the Pole. "So that's a good sign for me."
Kvitova said she would have to play even better against Wozniacki, including reducing the 38 unforced errors she had against Radwanska.
"It's important to have less unforced errors, but it's part of my game," she said. "I am a player who is going for the winners, so I have to accept the unforced errors, too. I shoot bullets on the court next time."
Wozniacki and Bartoli had a similar sloppy start, with six breaks of serve in the first set. Bartoli came from 4-2 down to win the first set. Wozniacki was almost untouchable in the second, and the third became back-and-fourth. Bartoli jumped out to 2-0 and then Wozniacki ran off five straight games. Bartoli won two straight to make it 5-4 but Wozniacki was able hold her nerve and serve out the match.
After her win, Diego Maradona, an ambassador for the Dubai Sports Council, came onto the court to give her one of his signed Argentina jerseys emblazoned with his No. 10. The Dane gave him a signed tennis racket.
"It was disappointing to lose that first set after I had been up," Wozniacki said. "But then I felt like she couldn't really do much in that second set because I was all over it. And in the third set, down 2-love, could have been 3-love and all of a sudden it's not looking too good. But I just kept fighting and every game was close."
Earlier, Vinci put away a mistake-prone Stosur, who lost in the quarterfinals in Doha last week following a galling second-round exit at her home Australian Open.
Stosur made 28 unforced errors and was broken twice in each set.
"Way too many errors," Stosur said. "She did well to not be bothered by anything I was trying to do. She used her slice very well which kept all the points neutral."
Despite the latest setback, Stosur felt she was improving over her dismal start to the year.
"January didn't really go as well as I wanted it to. I wasn't playing up to the standard and level that I think I'm capable of," she said. "The last couple of weeks, it's gotten better. I've played many more good matches than bad."
Vinci also ousted sixth-ranked Angelique Kerber. Her coach told her to attack Stosur's backhand.
"She (Stosur) has an unbelievable forehand, so I tried to play against her backhand because she has a lot of problem with backhand, and try some slice and also some top when I have time," Vinci said.
Vinci said her success in doubles -- the Italian has 19 doubles titles to only seven singles -- has contributed to her resurgence in singles, where she was ranked 17th.
"In doubles, you can try something that you can play in singles," she said. "I probably play more relaxed and then I play better in the singles."