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 Friday 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 Wimbledon, Bartoli was in obvious discomfort as she walked to the courtside chairs for treatment.
"Obviously 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," Bartoli said. "I can't be winning after winning after winning without feeling at some point a kind of exhaustion."
The players seeded No. 3-5 also advanced to the quarters. Third-seeded Agnieszka Radwanska beat American Sloane Stephens 6-1, 7-6 (2), No. 4 Li Na of China had a 3-6, 6-1, 7-6 (5) victory over Serbia's Ana Ivanovic and No. 5 Sara Errani of Italy beat Alize Cornet of France 7-5, 7-6 (3).
