Serena Williams (USA) returns a ball against Andrea Petkovic (not pictured) during the Rogers Cup tennis tournament at Aviva Centre in Toronto, Aug 13, 2015. [Photo/Agencies]

TORONTO - Top-ranked Serena Williams advanced to the Rogers Cup quarterfinals 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 titles 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. 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.