Number 10 seed Victoria Azarenka today collapsed on court during her second-round match against Gisela Dulko at the US Open.
On another sweltering day in New York, with temperatures again expected to approach 100 degrees fahrenheit, Azarenka slumped to the ground while serving at 15-30 and 5-1 down on the Grandstand Court.
Medical staff rushed to treat the 21-year-old from Belarus, who was then taken off the court in a wheelchair.
Azarenka had appeared to be struggling as early as the third game of the match when she received treatment for an arm injury but also looked to be suffering from blurred vision.
Speaking about the incident, Dulko said: "After that you don't think about tennis, you are just worried about your opponent.
"Now she has gone to the hospital so I guess it's something serious and I hope she is feeling good soon."
Asked about the conditions, Dulko added: "I'm used to this kind of weather but on the first day when I went to practice I was feeling dizzy as well.
"It's hard to play in these conditions and today I am much better because I have been here a few days, but it's tough."