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Winston-Salem, NC (Sports Network) - Third-seeded and two-time defending champion John Isner pulled out of the Winston-Salem Open on Monday, citing a hip injury.

The towering North Carolina native hails from nearby Greensboro.

Isner was a runner-up against former world No. 1 star Rafael Nadal at the ATP Masters 1000 event in Cincinnati on Sunday. The surging American recently titled in Atlanta and was also a hardcourt runner-up in Washington, D.C., earlier this month.

The 6-foot-9 Isner bested this week's top seed and former Wimbledon runner-up Tomas Berdych in last year's Winston-Salem finale at Wake Forest University.

Winston-Salem serves as a final tune-up for the U.S. Open.