Stanford: Belgian top seed Kim Clijsters overcame a mid-match slump to battle past Russia’s Vera Zvonareva 6-2, 3-6, 6-1 in the quarter finals of the Bank of the West Classic on Friday.

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 takes on French teenager Tatiana Golovin after both players recorded straight-sets victories.

In winning her 10th straight match at the event, three-time 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. (Reuters)