Fourth seed Justin Henin-Hardenne beat Argentine qualifier Mariana Diaz-Oliva 6-1 6-3 in the Rogers Cup.
The Belgian, champion in Toronto in 2003, played with a wrapped right hamstring, but it did not hinder her.
Fifth seed Serena Williams has been forced to withdraw from the tournament, though, after injuring a knee.
In other matches, seventh seed Kim Clijsters beat Virginie Razzano 6-3 6-0, and fourth seed Nadia Petrova beat Sesil Karatantcheva 4-6 6-1 6-4.
Nicole Vaidisova upset 10th seed Nathalie Dechy 6-2 6-4, and Spain's Conchita Martinez beat 15th seed Dinara Safina 7-5 6-2.
Henin-Hardenne played down any injury fears despite the tape on her thigh.
"It's getting better," she said.
"But you'll see me playing with my tape probably through the end of the year, because my doctor told me that I really have to take care of this because it's not 100%.
"I know that it's maybe going to bother me in the next few weeks, next few months."
Fellow Belgian Clijsters, who has had her fair share of injury problems, was delighted with her straightforward win over Razzano.
"This was perfect to get into it," she said. "I'm just happy to be on the court and happy to be playing in Toronto again."
Williams preparation for the US Open just 12 days away, suffered a serious blow.
Playing for the first time this week since her third-round defeat at Wimbledon, Williams said her ankle injury triggered a sore left knee which prevented her from continuing.
"Because of my ankle injury I had to take some time off so my leg isn't as strong as it needs to be," said Williams.
"So the pain in my knee is a result of that."
Williams has now failed to reach a final in any tournament since lifting the Australian Open in January.