Miami - Indian Wells champion Bianca Andreescu retired from her fourth-round match at the Miami Open while trailing Anett Kontaveit 6-1, 2-0 Monday.
Andreescu called a medical timeout after the first set to receive treatment on her right shoulder. She received similar treatment during her third-round victory over Angelique Kerber, who afterward told Andreescu she was the "biggest drama queen ever."
Andreescu, an 18-year-old Canadian, defeated Kerber in the Indian Wells final on March 17 for her first career title.
The No. 21-seeded Kontaveit was joined in the Miami quarter-finals by Petra Kvitova, who faced only one break point and beat Caroline Garcia 6-3, 6-3.
Kvitova, a two-time Wimbledon champion, is ranked a career-high No. 2 and will rise to No 1 if she wins the title.
Results on Monday from the Miami Open WTA/ATP Masters hardcourt tournament (x-denotes seeds):
Kevin Anderson (RSA x6) bt Joao Sousa (POR) 6-4, 7-6 (8/6)
Jordan Thompson (AUS) bt Grigor Dimitrov (BUL x24) 7-5, 7-5
Daniil Medvedev (RUS x13) bt Reilly Opelka (USA) 7-6 (7/5), 6-7 (5/7), 7-6 (7/0)
Roger Federer (SUI x4) bt Filip Krajinovic (SRB) 7-5, 6-3
Denis Shapovalov (CAN x20) bt Andrey Rublev (RUS) 6-3, 7-6 (7/5)
David Goffin (BEL x18) bt Marco Cecchinato (ITA x14) 6-4, 6-4
Hsieh Su-Wei (TPE x27) bt Caroline Wozniacki (DEN x13) 6-3, 6-7 (0/7), 6-2
Anett Kontaveit (EST x21) bt Bianca Andreescu (CAN) 6-1, 2-0 (ret)
Petra Kvitova (CZE x3) bt Caroline Garcia (FRA x19) 6-3, 6-3
Ashleigh Barty (AUS x12) bt Kiki Bertens (NED x7) 4-6, 6-3, 6-2
Simona Halep (ROM x2) bt Venus Williams (USA) 6-3, 6-3
Wang Qiang (CHN) bt Wang Yafan (CHN) 7-5, 6-4