After hitting his drive well to the right on the seventh hole, Woods called for an official. He hit his second shot and grimaced, then walked to the middle of the fairway to shake hands with playing partner Jason Bohn before leaving on a golf cart.
Woods had his head bowed for several minutes as he sat in front of his locker, and other times kept his eyes closed as if he were in the middle of a nap before answering questions from three reporters. At one point, he slammed his golf shoe to the ground.
"I've been playing through it," Woods said quietly. "I can't play through it anymore."
He said he first felt the injury before the Masters and plans to have an MRI next week. He said he was having a hard time with the pain, and that there was a tingling sensation on his right side down to his fingers. As he was driven off in a golf cart, Woods continuing squeezed his right hand and released his fingers.
"I might have a bulging disk," he said. Woods said he does not know what caused the injury, only that "playing doesn't help it."
Woods left the locker room and headed to a physical therapy trailer. He spent 37 minutes inside, then got whisked away from the course in a black SUV.
It is the first time he has withdrawn from a tournament since the Nissan Open at Riviera in 2006, when he narrowly made the cut and withdrew from the final two rounds because of the flu. He also withdrew from the 1995 U.S. Open at Shinnecock Hills has a 19-year-old amateur because of a wrist injury from hitting out of deep rough.
Woods started the final round 10 shots out of the lead and was 2 over through six holes.
It was only his third tournament back from a five-month hiatus after he was caught having extramarital affairs. Woods tied for fourth at the Masters, then missed the cut last week at Quail Hollow with the second-highest round (79) and the highest 36-hole score (153) of his PGA Tour career.
Woods at times stretched and rolled his neck between shots over the last three days, when he produced some good golf along with some shots that didn't remotely resemble the No. 1 player in the world. He popped up two tee shots with his 3-wood, and hit another one at a 45-degree angle. In relatively easy scoring conditions, Woods had rounds of 70-71-71 and was tied for 45th going into the last round.
Whether Woods keeps his No. 1 ranking now depends on Phil Mickelson, who tees off later Sunday.