Karolina Pliskova reaches Rogers Cup quarters after Osaka retires

The 19-year-old qualifier, ranked 50th in the world, had been giving Pliskova a mighty battle, winning a second set tie-break, but then after being broken to open the third suddenly called for the trainer and a few moments later retired trailing 6-2 6-7(4) 1-0.

"I was just trying to stay in the game, the first game of the third set was very tough I didn't even know she was injured."

Pliskova, playing in her first tournament since a shock second round defeat at Wimbledon, had shown some signs of rust in a ragged 6-3 6-3 win over Anastasia Pavlyuchenkova in her Rogers Cup opener, but looked more like a world number one as she swept four straight games to take the first set from Osaka.

But Osaka would not be rattled, matching the lanky Czech shot-for-shot in a gripping second set then dominating the tie-break 7-4 to level the match.

During the changeover Osaka told her coach that she was feeling discomfort and was told that if the pain persisted to withdraw and avoid the risk of further injury.

Osaka did just that, calling for the trainer after dropping serve to open the third.

"I think my game today was much better, especially my serve," said Pliskova, who pounded 13 aces past her opponent. "I didn't lose my serve in this match today, I'm happy with the way I was serving today."

It was a tough day on the Canadian hardcourts for the younger generation as 18-year-old American Catherine Bellis also saw her tournament come screeching to a halt with a 6-4 6-2 loss to France's Caroline Garcia.