Azarenka slumped to the ground while trailing Argentina’s Gisela Dulko 5-1 on the Grandstand court and was taken off court in a wheelchair and treated in hospital where she was diagnosed with a mild concussion.
“I was warming up in the gym prior to my match against Gisela Dulko when I fell while running a sprint. I fell forward and hit my arm and head,” Azarenka said in a statement.
“I was checked by the medical team before I went on court and they were courtside for monitoring. I felt worse as the match went on, having a headache and feeling dizzy. I also started having trouble seeing and felt weak before I fell.”
The 21-year-old Belarussian, wearing a black dress in temperatures nearing 90 Fahrenheit (32 Celsius), showed few signs of any medical problem as she came on court to warm-up.
But she lost her opening two service games and called the trainer as early as the third game. She received treatment to her injured arm and also complained of blurred vision.
It became increasingly clear that she was in difficulty as she took time out between every subsequent point and was ill at ease on her feet.
Then, while serving for the fourth time in the match, she collapsed on the baseline, leading to gasps from the crowd and a rush of medical staff onto the court who placed a white towel over her legs.
“I was scared,” Dulko told reporters after witnessing her opponent receiving treatment on the court before being taken away in a wheelchair as a medical official checked her pulse.
“She went to the floor – I was worried for her. I went to see her, brought her some ice, did whatever I could to help.”
This is Azarenka’s second retirement from a grand slam event. Having taken a set off Serena Williams at last year’s Australian Open, she pulled out citing dizziness and illness.
Dulko now faces 20th seed Anastasia Pavlyuchenkova in the third round – Reuters