Published: Aug 04, 2011 7:00 PM EDT
Updated: Aug 05, 2011 6:30 AM EDT

RENO, Nev. (AP) - Defending champion Matt Bettencourt has withdrawn from the Reno-Tahoe Open because of a rib injury.

Bettencourt got off to a good start Thursday morning with birdies on two of his first four holes at Montreux Golf & Country Club. He was 2-under through six when he was injured while hitting his drive on the next hole. He says the pain dropped him to his knees.

Bettencourt went on to bogey the next two holes before withdrawing. He says he doesn't know how serious the injury is.

Bettencourt became the seventh player a year ago to claim his first PGA Tour victory at Reno.

John Daly, Justin Leonard, David Duval and Boo Weekley are among those in this year's field on the mountain course designed by Jack Nicklaus.