Jie ZhengFifth seeded Jie Zheng of China advanced to the Semifinals of the 2010 WTA Polsat Warsaw Open Thursday when No. 2 seed, Caroline Wozniacki of Denmark could no longer continue after the 1st set due to pain from an ongoing ankle injury. The matched ended “6-3 retired”.

Caroline sprained her right ankle in the semifinals in Charleston on April 17, and has gone 2-4 since then, with losses to Lucie Safarova, Maria José Martinez Sanchez, and Alona Bondarenko. She is playing with her ankle taped.

After the match Caroline said: “I sprained my ankle in Charleston and it has been bothering me since then. I felt some pain from the beginning of the match today. I spoke to the physio and she said it would only get worse. I’m really sad. I wanted to win this match. I wanted to win the whole tournament. But health is the most important thing, and I didn’t want to risk having a worse injury.”

Jie will next play qualifier, No. 202 ranked Greta Arn from Hungary on Friday in the Semifinals.

Na LiAlso on Thursday, 3rd seeded Na Li of China easily advanced with a win over Sara Errani of Italy 6-2, 6-1.

Na had defeated Sara in the 1st round in Stuttgart on April 27 by a similar score, 6-1, 6-1. Na said: “I just played

[Sara] in Stuttgart, but my coach told me this morning the court here is very different from there. I just had to concentrate on every point and I did that. I played consistently.”

Na will now play the defending Warsaw champion, unseeded No. 38 Alexandra Dulgheru from Romania in the Semifinals on Friday.