NEW YORK, NY, USA - The first match on Louis Armstrong Stadium saw No.10 seed Victoria Azarenka's exit from the tournament, although in very different and unfortunate circumstances. With Gisela Dulko up 5-1 in the first set, Azarenka collapsed on the court and was taken off in a wheelchair.

Azarenka later commented on the retirement: "I was warming up in the gym prior to my match against Gisela Dulko when I fell while running a sprint. I fell forward and hit my arm and head. I was checked by the medical team before I went on court and they were courtside for monitoring. I felt worse as the match went on, having a headache and feeling dizzy. I also started having trouble seeing and felt weak before I fell. I was taken to the hospital for some medical tests and have been diagnosed with a mild concussion."

Read Azarenka's statement from later in the day, posted on her website.

Dulko faces No.20 seed Anastasia Pavlyuchenkova in the third round.