Top-ranked Serena Williams advanced to the Rogers Cup quarterfinals in Toronto 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 titles in 2001, 2011 and 2013.
Second-seeded Simona Halep of Romania advanced, outlasting 13th-seeded Angelique Kerber of Germany, 6-3, 5-7, 6-4.
Halep will face sixth-seeded Agnieszka Radwanska of Poland, a 6-2, 4-6, 6-4 winner over Alize Cornet of France.
In Rogers Cup play in Montreal, top-ranked Novak Djokovic beat American Jack Sock, 6-2, 6-1. The Serb, the tournament champion in 2007, 2011 and 2012, has won 50 of 53 matches this year.
Second-seed Andy Murray advanced, beating Luxembourg's Gilles Muller, 6-3, 6-2, and seventh-seeded Rafael Nadal of Spain beat Russia's Mikhail Youzhny, 6-3, 6-3.
Nick Kyrgios lost to American John Isner a day after insulting French Open champion Stan Wawrinka during a match.
The 16th-seeded Isner beat Kyrgios, 7-5, 6-3, in a third-round match marred by Kyrgios' shouting match with a fan.