(AP Photo/Chuck Burton)
WINSTON-SALEM, N.C. (AP) John Isner's preparations for the U.S. Open hit a setback Thursday when a sprained ankle forced him to withdraw from the Winston-Salem Open hours before his quarterfinal.
Isner, seeded 13th for next week's tournament at Flushing Meadows, was to have played Lukas Rosol of the Czech Republic.
At No. 15, Isner is the highest-ranked American in the U.S. Open. He is to face Marcos Giron, the 2014 NCAA singles champion, in the first round.