Jason Dufner won't defend title

— -- LOUISVILLE, Ky. -- Defending champion Jason Dufner pulled out of the PGA Championship after 10 holes Thursday because of a lingering neck injury and said he was done for keeps trying to play through the pain.

"I won't play golf again until I'm healthy," he said. "That could be at The Barclays. That could be next year. That could be 2016. I refuse to be out here and not be healthy. You're not giving yourself a chance to be competitive."

Dufner is eighth in the Ryder Cup standings and took an epidural on July 28 in an attempt to alleviate the pain and qualify for the American team. He described the injury as "an arthritic, degenerative issue that I'm probably going to be dealing with for a good bit," and said it started bothering him at the Masters.

As he stood in the Valhalla players parking lot Thursday evening after shooting 8-over for his 10 holes, Dufner said his neck had been "bothering me all day" and that it flared up on the practice range before his afternoon tee time.

"Just overall fatigue," he said of how he felt during the round. "Tired, shoulder tightness, numbness, dead arm, no feeling in my left hand."

The potential loss of Dufner could leave U.S. Ryder Cup captain Tom Watson with several prominent holes to fill, as Dustin Johnson deals with his personal issues away from the tour and Tiger Woods continues to struggle in the wake of back surgery. Another American star, Matt Kuchar, withdrew from the PGA Championship with back spasms on Thursday.

Dufner said he tried ice, pills, injections -- "you name it" -- in combating the neck injury.

"I've done it for the last month," he said. "The only thing I haven't done is take significant time off."

Before stepping into a silver Mercedes SUV and driving himself away from Valhalla, Dufner maintained that surgery is not an option.

"Nobody's mentioned that," he said. "I don't think I would have surgery, to be honest with you. Quality of life isn't very good when you have neck surgery. You start having other problems."

When the problems became too much to bear in the middle of his round, punctuated by a triple-bogey at the par-5 10th, Dufner shook hands with playing partners and fellow PGA champions Keegan Bradley and Y.E. Yang and called off his defense of the title.

"I was trying to get healthy for these last couple of weeks for a pretty good run here at Firestone and the PGA," he said, "and I wasn't able to do it. I've done everything I can. There's no point to be out there hacking it around."