Sharapova, trailing 3-4, twisted her left ankle in the eighth game against the Czech fifth seed, who beat her in the Wimbledon final in July.

"I landed awkwardly on my left ankle. I felt a sharp pain and the next thing I knew I was on the floor," the Russian said.

"It swelled up immediately and I knew there was no way I could continue."

Kvitova faces Vera Zvonareva in the semi-finals after the Russian beat compatriot Maria Kirilenko 6-3 6-3 in their quarter-final.

Third seed Victoria Azarenka beat Marion Bartoli 7-5 6-0 to set up a semi-final clash against Poland's Agnieszka Radwanska who beat Estonia's Kaia Kanepi 6-2 7-6.