Injury forces Sharapova to retire in Tokyo QF

An ankle injury forced Maria Sharapova to retire from her quarterfinal match against Petra Kvitova at the Toray Pan Pacific Open in Tokyo on Thursday. The Russian second seed was 4-3 down in the first set to the Czech fifth seed when she pulled out. \"Maria went over on her left ankle while serving, and, after a brief medical time-out, decided that she could not carry on,\" a message on her website said. Sharapova, who won the French Open this year, is world No. 2 and enjoying her best season since a shoulder injury saw her drop out of the top 100 in 2009. Kvitova, the Wimbledon champion, walks over into a semifinal against Vera Zvonareva, the No. 4 seed who beat another Russian, Maria Kirilenko 6-3, 6-3 earlier Thursday.