Tenth-seeded Victoria Azarenka, who collapsed during her match against Gisela Dulko Wednesday, is still at a local hospital according to U.S. Open tournament referee Brian Earley. Earley said Azarenka retired from the match, where she trailed 5-1, "with headache-like symptoms. She was taken to a nearby hospital for diagnostic testing. Out of respect to her privacy, we can not give any more details. However, we can say that this does not seem to be primarily a heat-related illness."
Extreme heat rules are in effect, allowing women to take a 10-minute break after two sets and allows men to ask for medical timeouts if needed. There have been a couple of instances of cramping though most players have said so far that though the heat is noticeable it isn't impossible.