Top seed Caroline Wozniacki defeated 6th seed Nadia Petrova 6-3, 6-4 Friday in Charleston, and is now into the semifinals. Her opponent will be 7th seed Vera Zvonareva, who defeated 13th seed Melanie Oudin, 7-5, 6-2. Oudin had a difficult time holding her serve, and Zvonareva was not serving at the level at which she is capable. She will certainly have to serve better against Wozniacki, if she expects to be truly competitive against the first seed.
4th seed Sam Stosur defeated Peng Shuai 6-4, 6-1. Peng, whose thigh was wrapped, appeared to have some trouble with her movement in the second set. Stosur, who had outstanding service percentages of 82 and 76, served for the match in style: She hit three consecutive aces, followed by a serve that was impossible to return.
In the doubles quarterfinal that was played Friday, first seeds Liezel Huber and Nadia Petrova defeated Melinda Czink and Sharon Fichman 7-5, 6-1.