Two-time defending champion Mardy Fish, the No. 2 seed, withdrew from the tournament with a right ankle injury. Fish was leading Gilles Muller of Luxembourg 6-4, 3-2 when he pulled out.
Isner will play 19-year-old Jack Sock, a 7-6 (5), 7-6 (5) winner over Steve Johnson in a matchup of wild cards.
Muller will face Australia's Matthew Ebden, who beat James Blake 6-7 (6), 6-4, 6-4.
In other quarterfinal matches Friday, No. 4 seed Andy Roddick faces Michael Russell and No. 3 seed Kei Nishikori of Japan plays countryman Go Soeda, the No. 8 seed.
John Isner
http://accesswdun.com/article/2012/7/250883