Clijsters sets up Vaidisova semi in Stanford

The defending champion moved on to face third seeded Czech Nicole Vaidisova, who overwhelmed Australia's Samantha Stosur 6-4 6-2 to reach the last four.

In Saturday's other semi-final, second seed Patty Schnyder of Switzerland [Images] takes on French teenager Tatiana Golovin [Images] after both players recorded straight-sets victories.

In winning her 10th straight match at the event, three-times champion Clijsters was almost unplayable in the first and third sets, adeptly defending her opponent's heavy blasts while peppering the corners with pinpoint forehands.

After dropping the first set, Zvonareva, who won in Cincinnati last week, grabbed control of the match with her searing groundstrokes in the second, but lost her focus in the third set while Clijsters soared.

"I was making too many unforced errors in that second set and I refocused," Clijsters told reporters

"I served more consistently and it gave me better opportunities to play aggressive.

"She plays aggressively, so if you don't, she can move you around. So when I got a chance to dominate from the first ball, I tried to go for it."

The 17-year-old Vaidisova hammered Stosur with big serves and blinding groundstrokes to ease to a routine win.

"I didn't start out the greatest, but I stayed positive and was able to come back and play well," Vaidisova said.

"I didn't have that much trouble with her serve and tried to change the pace sometimes. I'm excited to be in the semi-finals."

Schnyder defeated American Jill Craybas 6-4 7-5 to set up her match against Golovin, who upset fourth seed Anna-Lena Groenefeld of Germany [Images] 6-4 7-6.

"I was very up and down," Schnyder said. "I was surprised at how well she hit her down the line forehand, but I served really well and feel pretty good about how I got through."

The 18-year-old Golovin continued her superb week, pounding to victory from the back court.

Golovin sustained a serious ankle injury in March that had her out of action for more than two months, but believes her recovery is now complete.

"She made a lot of winners and mistakes so it was tough to get a rhythm," Golovin said.

"I adapted pretty well to her. In the tiebreaker she broke down mentally and that's good for me."

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