Australian Sam Stosur has been bounced out in the second round of the Rogers Cup in Montreal, beaten in straight sets by unseeded Russian Daria Kasatkina.
Stosur, seeded 13th for the WTA tournament, struggled with her service game as she sent down nine double faults in the 7-6 (7-1) 6-3 loss.
Comparatively, world No.33 Kasatkina served eight aces in the win, and will go on to meet Italian Roberta Vinci who beat compatriot Giorgi Camila.
Venus Williams opened play with a 6-3 6-0 victory over Barbora Strycova.
Playing her last event before the Rio Olympics, the 36-year-old Williams finished off the overmatched Czech player in 58 minutes.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Williams was coming off a loss to Britain's Johanna Konta on Sunday in the final of the Bank of the West Classic in California.
"It was definitely more straightforward than some of our other matches," Williams said.
"I'm never happy with my matches. Even an easy scoreline is never enough. But it's about figuring out how to win instead of playing perfect."
The seven-time Grand Slam champion, seeded sixth, gave up 10 points in the 24-minute second set.
The only hiccup for Williams was the seventh game of the first set. Up 4-2, she had her serve broken.
"I just needed to stay focused," said Williams. "A 4-4 is definitely different than a 5-3. But it wasn't necessarily a turning point, because there are matches where I've been down and came back, and vice versa, so you realise that the match isn't over until it's over."
Williams will face Madison Keys in the next round. Keys beat fellow American Madison Brengle 6-4 6-3.
