SYDNEY, Australia - Sydney's battle for No.1 took an unexpected turn on Wednesday, as current No.1 Caroline Wozniacki was upset in the quarters by Agnieszka Radwanska. Petra Kvitova can take No.1 by winning the title.

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Wozniacki, who had beaten Radwanska five times in a row, served for the match at 63 54 but was unable to close it out. Radwanska won, 36 75 62.

Wozniacki was struggling with her wrist during the loss. "I could feel it today, especially in the third set. I felt it more as the match went on. I hope it's not serious. I'm going to go and get it checked out tomorrow. Let's just hope for the best. I should be completely fine for the Australian Open next week."

Kvitova had few problems in her match, winning the first eight games against Daniela Hantuchova then closing her out after a close second set, 60 64.

"I was surprised I played that well. I'm really happy with the first set," Kvitova said. "I played well in the second set also but it was closer because Daniela was playing much better. Fortunately I made it through the second set."

Coming into the tournament, Kvitova would become No.1 if she won the title - that scenario stands, it's just Wozniacki can't be the one to stop her now.

"It's still two matches away, and the next one will be really tough, so we'll see what happens. I'm still not really thinking about it," Kvitova declared.

"The most important thing for me is being healthy, being able to play, and being able to play well," Wozniacki said. "What happens happens."

Awaiting the No.2-seeded Kvitova in the semifinals will be No.4 seed Li Na, who cruised through the first set then won a marathon 73-minute second set against Lucie Safarova, 62 76(3). "Now I'm feeling much, much better than I did in the last half of 2011," said Li, who is the defending champion in Sydney. "I feel stronger and more fit right now. I was happy how I moved on the court and to come to the semis in my first tournament of the year feels really good."

Radwanska, the No.7 seed this week, will play No.3 seed Victoria Azarenka, who rallied from 5-2 down in the first set and twice was a break down in the second set but managed to squeak both out against No.8 seed Marion Bartoli, 75 64. "I saw her playing in Hopman Cup before and she was really solid. She played some incredible tennis today," Azarenka said. "We always have tough matches, so I was expecting a tough battle. It was a great test."

Kvitova and Li are tied in their head-to-head, 1-1, while Azarenka leads Radwanska in their head-to-head, 5-3 (Radwanska won the last time).