Matt Kuchar withdrew from the PGA Championship shortly before his tee time on Thursday morning due to back spasms.
Kuchar, who won the Heritage earlier this year, was coming off a tie for 12th at the WGC-Bridgestone Invitational. His win in Hilton Head in April ended a run of four straight top-5 finishes for Kuchar.
The world No. 6 leads the PGA Tour in top-10 finishes with 10 in 20 starts this season. Among those 10, he also had five top-5 finishes, which is tied for second-most on tour.
Kuchar had made the cut in three of his six PGA Championship appearances, with a tie for 10th in 2010 being his best finish.
The 36-year-old was replaced in the field by John Huh, who tied for third last week at the Barracuda Championship. Prior to that, Huh had missed the cut in four of his previous five starts.