Ninth seed Daniela Hantuchova was upset 6-4 3-6 6-1 by Ukrainian Julia Vakulenko, another shock in the first round of the US Open.
The Slovak made 32 unforced errors as she suffered her earliest exit at Flushing Meadows since she lost on her debut in 2001.
"I felt fine here," Hantuchova said. "I felt very good. Today was just one of those things that is hard to understand."
"I had my opportunities but I think she played very well, especially in the third set. I had my chances and didn't take them."
However, the world No.11 still harbors hopes of qualifying for the season-ending Sony Ericsson Championships, an event in which only the top eight-ranked players take part.
"It's going to be tough but I still have chances. I may add a couple more tournaments to my schedule if I am doing well." (via Reuters)