(CNN) -- Tenth seed Victoria Azarenka retired from her second round match at the U.S. Open after collapsing in soaring temperatures.
Azarenka, from Belarus, was trailing 5-1 in the opening set of her second round match against Argentina's Gisela Dulko in temperatures of nearly 100 degrees Fahrenheit when she crouched down after a rally.
Seconds later she slumped to the floor as medics rushed out to treat her before she was taken from the court in a wheelchair, but Azarenka later said she was suffering from concussion.
In a statement on the WTA Tour's official website she said: "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.
"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. I was taken to the hospital for some medical tests and have been diagnosed with a mild concussion".
CNN
