Harris English, a U.S. Ryder Cup team member and the 25th-ranked player in the Official World Golf Ranking, withdrew from next week's PGA Championship on Friday.
English underwent surgery in February to repair the labrum in his right hip and has not fully recovered. He last played on the PGA Tour in mid-January.
English, 32, won two tournaments last season — the Sentry Tournament of Champions and the Travelers Championship, the latter in an eight-hole playoff against Kramer Hickok.
In an ironic twist, Hickok was the first alternate for the PGA Championship and now replaces English in the field.
South African Charl Schwartzel, the 2011 Masters champion who tied for 10th at last month's Masters, moved up to first alternate status. He would be chosen for the field if another golfer drops out before the first round.
The PGA Championship will be played May 19-22 at Southern Hills Country Club in Tulsa, Okla.
