Kateryna Bondarenko Kateryna Bondarenko from Ukaraine pulled a huge upset in round one of the U.S. Open, defeating No. 8 seed, Na Li of China.

Li admitted she wilted in the stifling heat with temperatures peaking at around 95 degrees Fahrenheit. “From the middle of the second set I was feeling the energy was going down,” Li told Reuters. “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, leveled the match and, as Li faded, roared through the decider to reach round two.

Bondarenko, ranked No. 59, won the match 2-6, 6-4, 6-2. It was her biggest victory since she defeated then No. 4 Elena Dementieva in the 2nd round in Tokyo last year 6-2, 6-&(3), 6-1. A few weeks earlier in Toronto, Bondarenko had defeated No. 3 Venus Williams in the 2nd round 1-6, 7-5, 6-4.

While she could be called an occasional giant-killer, this year she has been struggling, compiling a record in 2010 of 6-12.