Defending champion Tiger Woods pulled out of the WGC-Bridgestone Invitational in Akron, Ohio during the final round on Sunday due to a back injury.
The former world number one and 14-times major champion made a double-bogey on the seventh hole and looked to be in pain after his drive at the ninth before deciding to retire on four over par, 18 shots behind overnight leader Sergio Garcia.
Woods was limping as he climbed into a golf cart and quickly left the course before issuing a short statement.
"It happened on the second hole when I hit my second shot. I fell back in the bunker... I just jarred it and it's been spasming ever since," he said.
The 38-year-old Woods, who has won the WGC-Bridgestone Invitational eight times, is due to play in the U.S. PGA Championship, the year's final major, starting on Thursday.
He said it was too early to speculate on whether he would be able to tee off in the U.S. PGA tournament at Valhalla Golf Club in Louisville, Kentucky.