Serena Williams' BNP Paribas Open campaign came to an end in the third round as she retired from her match against Garbine Muguruza due to illness while trailing 6-3 1-0.
After a first set in which she had led 3-0, Williams had a lengthy conversation with the trainer and doctor but no medical timeout was taken.
Then, after a love hold from Muguruza, the 37-year-old American walked to the chair and sat down, breathing heavily, supervisor Donna Kelso came over for a discussion and the retirement was subsequently confirmed.
It later said on the official WTA Twitter feed that the official reason for the retirement was "viral illness".
Muguruza's opponent in round four will be Kiki Bertens, who beat Johanna Konta 7-6 (12-10) 6-4.
