TORONTO (AP) " Karolina Pliskova advanced to the quarterfinals at the Rogers Cup on Thursday when Japanese qualifier Naomi Osaka was forced to retire because of an injury.
The world's top-ranked player moved on with a 6-2, 6-7 (4), 1-0 victory when Osaka quit with an abdominal complaint.
It wasn't immediately clear when Osaka suffered the injury. She was in form during the tiebreaker, firing a service winner to convert her second set point under the warm sun at Aviva Centre.
Pliskova came out strong to open the third set and Osaka called for a trainer at the changeover. She briefly stretched out on the hardcourt before the decision was made.
Pliskova, meanwhile, will move on to play sixth-seeded Caroline Wozniacki of Denmark, who beat 10th-seeded Agnieszka Radwanska of Poland 6-3, 6-1.
Caroline Garcia of France defeated American Catherine Bellis 6-4, 6-2 in the other early singles match.
Later Thursday, second-seeded Simona Halep of Romania was to meet Barbora Strycova of the Czech Republic. Third-seeded German Angelique Kerber was to play American Sloane Stephens and Ekaterina Makarova of Russia was to face Lucie Safarova of the Czech Republic.
American Venus Williams, the ninth seed, will play fifth-seeded Ukrainian Elina Svitolina in the feature evening matchup. In the late match, Australian qualifier Ashleigh Barty was to meet fourth-seeded Garbine Muguruza of Spain.