Serena Williams was forced to retire with a viral illness in her third round match with Spain’s Garbine Muguruza at Indian Wells on Sunday.
The 37-year-old, who on Friday celebrated 12 months since her return to the court following pregnancy, made a strong start by pushing 3-0 in front.
But two-time grand slam champion Muguruza won six straight games before Williams called for the trainer, looking in clear discomfort and breathing heavily.
“Before the match I did not feel great and then it just got worse with every second – extreme dizziness and extreme fatigue,” the American said in a statement.
“By the score it might have looked like I started well, but I was not feeling at all well physically.”
Williams wanted to play on but after losing a seventh game in a row, the 23-time grand slam winner conceded a 6-3, 1-0 defeat.
“It’s never good to see someone that’s not feeling well on the court so I wish to see her soon and better,” Muguruza said.
Muguruza moves on to the last 16 where she will play Dutch seventh seed Kiki Bertens who prevailed 7-5, 6-4 against Briton Johanna Konta.
Earlier in the women’s draw, number two seed Simona Halep fought off five breaks from Ukraine’s Katerina Kozlova to win 7-6 (7-3), 7-5 for a place in the last 16.
Halep will face Marketa Vondrousova in the next round after the Czech battled past Latvian Jelena Ostapenko in three sets with a 4-6, 6-3, 6-4 victory.
Ukraine’s Elina Svitolina advanced with a 7-5, 6-4 result against Australian Daria Gavrilova and meets another Australian in Ashleigh Barty who dispatched American Jennifer Brady 6-3, 6-2.