Williams cruises past Petkovic

World number one Serena Williams had little trouble progressing to the quarter-finals of the Rogers Cup as she eased past 16th seed Andrea Petkovic 6-3, 6-2 on Thursday. 

Williams and Petkovic managed to hold serve for the first seven games of the set before Williams extended her lead to 5-3 when she broke Petkovic in the eighth game. 

After establishing some breathing space the 33-year-old, who has won all three grand slams this year, proceeded to clinch the first set. 

Williams began the second set strongly and broke Petkovic in the opening game en route to taking a 2-0 lead. 

The world number one continued to remain one step ahead despite Petkovic's best efforts. However, after being broken again in the seventh game, Petkovic's fight dwindled and the 16th seed was eventually knocked out of the tournament in just over an hour. 

Williams will face Roberta Vinci in the quarter-finals after the Italian triumphed over Daria Gavrilova 6-4, 6-3. 

Second seed Simona Halep, fifth seed Ana Ivanovic, sixth seed Agnieszka Radwanska and 15th seed Sara Errani all booked their spots in the quarter-finals, while Lesia Tsurenko and Belinda Bencic also advanced to the last eight.