British number two Heather Watson was forced to pull out of her Dongfeng Motors Wuhan Open first-round match with Madison Brengle after complaining of feeling dizzy and having double vision.
Watson was trailing 3-6 1-2 to her American opponent in sweltering conditions in China when she decided she could no longer go on.
She had called a medical time out after losing the first set and a doctor was called on to court to take her blood pressure in some worrying scenes reminiscent of her first-round US Open defeat last month.
However, she tried to play on and came out swinging in the second set before her symptoms got the better of her.
The 24-year-old had played twice on Saturday in similar mid-30s temperatures to get through qualifying and make it to the main draw.
After that she insisted she was feeling fit following her episode in Flushing Meadows where she went for blood tests after saying her symptoms were similar to when she suffered from glandular fever.
She told Press Association Sport on Saturday: "I got the blood test results and they are all fine, I am very healthy. I just think it was a mixture of things, maybe stress and anxiety and the heat is always a factor.
"But I feel as if I am fit, I train in Florida, so I was fit and ready, I think it was just the other things that affected me."
Source: PA
