Wozniacki fights off injury and Cibulkova

“I decided straight away after I felt it,” she said. “I played one more point and decided I needed to see the trainer because I felt a sharp pain in there. I needed to treat it.”

The Danish third seed, who is set to be the eighth seed in next week’s US Open, defeated Slovakia’s Dominika Cibulkova 6-2, 6-1 in the quarter-finals and remained unbeaten at New Haven, improving to 20-0. But Wozniacki felt a twinge in her right knee during the first game of the second set and called for a trainer.

After a Cibulkova double fault on the next point, Wozniacki walked to the chair umpire and pointed to her knee. She sat down and got a bag of ice from a cooler.

She continued with the knee wrapped and won with ease, improving to 8-3 all-time against Cibulkova, but planned to have the knee examined before deciding if she would play on Friday.

Wozniacki is scheduled to face Russian seventh seed Maria Kirilenko, who beat Olga Govortsova of Belarus 6-1, 6-2 in another quarter-final Thursday. On the other side of the draw, Czech star Petra Kvitova clinched the US. Open Series title with her quarterfinal win over Lucie Safarova.

The world’s fifth-ranked player had little trouble with her friend and compatriot, recording 10 aces and no double-faults in a 6-3, 6-3 win. The series championship, based on points earned in five U.S. hardcourt tournaments this summer, makes Kvitova eligible for a bonus of up to $1 million depending on her finish in next week’s US Open.

“I’m really proud that I’m champ,” Kvitova said. “Money is not the important thing in the world and in the life. So I’m so glad that I played a lot of matches, good matches. I have great results. I’m here in the semi-final. That’s important for me to have some confidence for the US Open.”