Top-ranked Serena Williams advanced to the Rogers Cup quarter-finals on Thursday night, beating 16th-seeded Andrea Petkovic of Germany 6-3 6-2.

The 21-time Grand Slam singles champion will face Italy’s Roberta Vinci, a 6-4 6-3 winner over Russia’s Daria Gavrilova.

Williams won titles in Toronto in 2001, 2011 and 2013.

Second-seeded Simona Halep of Romania also advanced, outlasting 13th-seeded Angelique Kerber of Germany 6-3, 5-7, 6-4 in hot afternoon conditions.

“I did well in the last game,” Halep said. “I said, ‘I have to win it because I cannot move anymore’.”

Halep will face sixth-seeded Agnieszka Radwanska of Poland, a 6-2 4-6 6-4 winner over Alize Cornet of France.

In the late match, fifth-seeded Ana Ivanovic of Serbia played Slovenia’s Polona Hercog.

Unseeded Belinda Bencic topped Sabine Lisicki 6-1 1-6 7-6 (7/3) to keep her run going.

The 20th-ranked player from Switzerland opened the tournament with a victory over slumping Canadian Eugenie Bouchard and followed it with an upset win over fifth-ranked Caroline Wozniacki of Denmark.

Bencic will play the Ivanovic-Hercog winner.

Also, 15th-seeded Sara Errani of Italy beat Belarus’ Victoria Azarenka 7-5 6-3 and Ukraine’s Lesia Tsurenko beat Germany’s Carina Witthoeft 6-3 6-4.