New York: China`s Li Na admitted she wilted in the stifling heat at the US Open on Tuesday as she suffered a shock 2-6, 6-4, 6-2 defeat to hard-hitting Ukrainian Kateryna Bondarenko.
With temperatures peaking at around 95 degrees Fahrenheit (35 Celsius), the eighth seed cruised through the first set but then lost her way as world number 59 Bondarenko stormed back to clinch victory in one hour 43 minutes.
"From the middle of the second set I was feeling the energy was going down," Li told reporters. "I talked to myself to stay positive on the court but it didn`t work."
Li looked on course for a straightforward win when she broke serve twice to win the first set. But Bondarenko, who has slipped down the rankings after a three-month absence with knee trouble, levelled the match and, as Li faded, roared through the decider to reach round two.
Li, who reached the quarter-finals in New York along with Bondarenko in 2009, was surprised that she was not able to cope with the intense conditions since she is from a hot climate.
"My home town (Wuhan) also is hot but I don`t know why (I felt so bad)," she said. "(The warm-up event in) Cincinnati was also hot and humid so maybe the body didn`t feel good in this weather."
It is only the second time Li has lost in the first round in the U.S. Open and she went into the event confident having reached at least the fourth round the past three years.
"I really wanted to try in the U.S. Open because I also had a good beginning to the year," she said.
"The whole year I was playing well and only in the US Open I lost in the first round. Maybe I am tired in the body and tired in the mind, I don`t know."
Bondarenko now plays either Dominika Cibulkova of Slovakia or Stefanie Voegele of Switzerland in the second round.