TOKYO (AP) -- Second-seeded Maria Sharapova was forced to retire because of an injury during the first set of her quarterfinal match Thursday against Petra Kvitova at the Pan Pacific Open.
With her Czech opponent leading 4-3 in the first set, Sharapova twisted her left ankle when serving in the eighth game. She limped to her chair and pulled out after speaking with her trainer.
It was a rematch of this year's Wimbledon final, where Kvitova beat Sharapova 6-3, 6-4 for her first major title.
Kvitova will now face fourth-ranked Vera Zvonareva of Russia, who defeated compatriot Maria Kirilenko 6-3, 6-3 in another quarterfinal.
Zvonareva had five aces in the match that lasted 1 hour, 14 minutes at Ariake Colosseum and improved to 6-0 in head-to-head matches against the unseeded Kirilenko.