MONTREAL (AP) -- Fifth-seeded Petra Kvitova rallied to beat Ksenia Pervak 4-6, 7-6 (0), 6-0 on Wednesday night in the second round of the Rogers Cup.
Kvitova, the 2011 Wimbledon champion, quickly finished off Pervak after the match was delayed for 30 minutes by rain with the players tied 4-4 in the second set.
In other second-round matches, fourth-seeded Sam Stosur led Simona Halep 7-5, 4-4 when Halep retired because of left thigh injury; eighth-seeded Sara Errani beat Jana Cepelova 6-3, 6-2, and 16th-seeded Lucie Safarova edged Sesil Karatantcheva 6-4, 6-4.
In first-round play, 18-year-old Canadian Eugenie Bouchard beat Shahar Peer 3-6, 6-2, 7-5. Americans Christina McHale and Varvara Lepchenko also won first-round matches. McHale beat Arantxa Rus 3-6, 6-1, 6-3, and Lepchenko topped Anastasia Pavlyuchenkova 6-2, 6-3.
Earlier, Maria Sharapova withdrew because of a stomach ailment. The second-ranked Sharapova told organizers she picked up the bug at the London Olympics, where she lost the final to Serena Williams. Sharapova was replaced in the draw by Galina Voskoboeva. McHale will face Voskoboeva in the second round.