Top-seeded Karolina Pliskova advances at Rogers Cup

Caroline Wozniacki, of Denmark, returns the ball against Agnieszka Radwanska, of Poland, during a women's third round match at the Rogers Cup tennis t

Agnieszka Radwanska, of Poland, makes a return against Caroline Wozniacki, of Denmark, during a women's third round match at the Rogers Cup tennis tou

Simona Halep, of Romania, returns the ball against Barbora Strycova, of the Czech Republic, during the Rogers Cup tennis tournament in Toronto on Thur

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 had to retire because of an abdominal injury.

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.

The world's No. 50 player received treatment after the match and did not speak to reporters.

Pliskova, meanwhile, will move on to play sixth-seeded Caroline Wozniacki of Denmark, who defeated 10th-seeded Agnieszka Radwanska of Poland 6-3, 6-1.

Second-seeded Simona Halep of Romania needed only 59 minutes to breeze by Barbora Strycova of the Czech Republic 6-1, 6-0 while American Sloane Stephens upset third-seeded German Angelique Kerber 6-2, 6-2.

Later Thursday, fifth-seeded Ukrainian Elina Svitolina defeated American Venus Williams 6-2, 6-1, and Spain's Garbine Muguruza beat Australian qualifier Ashleigh Barty 6-0, 3-6, 6-2.

Also, Caroline Garcia of France advanced with a 6-4, 6-2 win over American CiCi Bellis, and Lucie Safarova of the Czech Republic moved on with a 6-3, 6-7 (3), 6-2 victory over Ekaterina Makarova of Russia.