While top players keep dropping around her, Serena Williams plows ahead at the women's Rogers Cup.

On a day that saw French Open champion Maria Sharapova and Wimbledon champ Petra Kvitova eliminated from the US$2.44 million hardcourt event, Williams served impeccably to defeat 15th-seeded Lucie Safarova 7-5, 6-4 in the third round on Thursday.

She is 7-0 in her career against the Czech left-hander.

The match played out from the service line, with one break in each set going to Williams. In the last game of the second, Safarova double faulted twice and the hit match point long.

"I served great," said Williams, who is celebrating her 200th week as the world No. 1 and who is coming off a win last week at Stanford. "I needed to serve great because she was hitting unbelievable serves to me."

Williams, who won last year in Toronto, is playing in Montreal for the first time since she retired with an injury in the final in 2000. For a second match in a row, the American delighted the crowd by doing her post-match interview at courtside in French.

The win set up a quarter-final on Friday between the two most impressive players in the tournament, Williams and Caroline Wozniacki, who routed American qualifier Shelby Rogers 6-1, 6-0.

Wozniacki, the 11th seed from Denmark who coming off a victory in Istanbul, has dropped only six games in three matches en route to the quarter-finals.

"It will be a great match," said Williams, who is 6-1 against Wozniacki. "She's playing great tennis.

"She's really focused. It will be a good match to see where I am."

Rogers caused the shock of the tournament when she ousted local favourite Eugenie Bouchard in the second round on Tuesday night. But the 113th-ranked American was no match for former world No. 1 Wozniacki.

"I felt really comfortable and confident," Wozniacki said. "I served and returned well.

"She's a tough player. She has some big shots. I was just able to neutralize them and play my game."

Carla Suarez Navarro upset fourth-seeded Sharapova 6-2, 4-6, 6-2 in a match delayed twice by rain.

And second seed Kvitova is out after a 6-4, 1-6, 6-2 loss to Ekaterina Makarova in a battle of left-handers.

Suarez Navarro, ranked 16th in the world, returned from the second delay to break Sharapova's service and then staved off a break point in the next game thanks to a lucky net cord. She broke again in the final game.

Sharapova said playing on centre court, which has more space on the sides and behind the baseline than a regular court, may have helped her Spanish opponent.

"I think that favoured her quite well as she was able to step so far behind the baseline and retrieve a lot of balls," said Sharapova.

Sharapova, just getting started on the hardcourt season, had struggled to a three-set win in her opening match Wednesday against Garbine Muguruza. She said she has much to work on in her game heading toward the U.S. Open at the end of August.

"I couldn't find my rhythm from the beginning of the match," said the 27-year-old. "I always had my back against the wall, always had to come back."