Serbia's Ana Ivanovic reacts during her match against Bulgaria's Tsvetana Pironkova in the fourth round of play at the 2012 US Open tennis tournament,  Monday, Sept. 3, 2012, in New York. (AP Photo/Kathy Willens)

Photo by: Kathy Willens

Serbia's Ana Ivanovic reacts during her match against Bulgaria's Tsvetana Pironkova in the fourth round of play at the 2012 US Open tennis tournament, Monday, Sept. 3, 2012, in New York. (AP Photo/Kathy Willens)