TORONTO -- Top-seeded Serena Williams advanced to the Rogers Cup quarter-finals Thursday, beating 13th-seeded Kirsten Flipkens of Belgium 6-0, 6-3.
Williams, coming off a tournament victory 2 1/2 weeks ago in the Swedish Open, set up a match today against Slovakia's Magdalena Rybarikova.
"She wasn't able to play her game as much as she wanted to," Williams said. "When you play such a high-ranked player, you have to go in there with the mindset of do the best you can before they can step all over you."
Wimbledon champion Marion Bartoli retired because of an abdominal injury early in the second set of her match against Rybarikova.
"Kind of excess of tiredness and exhaustion on my body," Bartoli said. "The pain is so large and we can't really say right now exactly (if) there is a tear at some point or if it's just like a huge tightness."
Rybarikova led 7-6 (5), 1-0 when the seventh-seeded Bartoli stopped playing.
Playing her first event since returning from a hamstring injury that sidelined her since her major victory in London, Bartoli was in obvious discomfort as she walked to the player bench area.
"Everything that happened for me since a month (ago), it's not without any tiredness," Bartoli said. "It took me so much energy to win my first Grand Slam that at some point I will have a kind of low and it's normal. I'm human. At the end of the day I can't be winning after winning after winning without feeling at some point a kind of exhaustion."
Earlier, fourth-seeded Li Na of China fought back from a three-game deficit in the final set for a 3-6, 6-1, 7-6 (5) victory over Serbia's Ana Ivanovic.
Third-seeded Agnieszka Radwanska of Poland also advanced to the quarterfinals, beating American Sloane Stephens 6-1, 7-6 (2). Fifth-seeded Sara Errani of Italy beat Alize Cornet of France 7-5, 7-6 (3); and Romania's Sorana Cirstea edged Serbia's Jelena Jankovic 6-3, 6-4.
-- The Canadian Press