WINSTON-SALEM - Two-time champion John Isner withdrew from the US Open tune-up event at Winston-Salem with a left ankle injury. The American was due to play Lukas Rosol in the quarter-finals on Thursday, but pulled out with the injury suffered in his win over Mikhail Kukushkin on Wednesday. "I am extremely disappointed to have to withdraw from the Winston-Salem Open, one of my favorite stops of the year," said Isner , who hails from North Carolina. Rosol advanced by walkover into a Friday semi-final against Taiwan's Lu Yen-Hsun, who defeated Italy's Andreas Seppi 6-4, 6-4. The other semi-final will match Poland's Jerzy Janowicz, who ousted Belgian David Goffin 6-4, 6-2, against American Sam Querrey, who rallied to eliminate Spanish fifth seed Guillermo Garcia-Lopez6-7 (3/7), 6-2, 6-4. AFP