Mardy Fish, the No. 23 seed, has withdrawn from the 2012 US Open due to health concerns. Roger Federer advances to the quarterfinals via walkover.
“I regret that I have to withdraw from the US Open for precautionary measures," Fish said in a statement. "I was reluctant to do so, but am following medical advisement. I had a good summer and look forward to resuming my tournament schedule in the fall.”