Former world No.1 Tiger Woods has blamed "deactivating" glute muscles after withdrawing midway through the first round of the US PGA Tour event at Torrey Pines in California.
Woods, who underwent back surgery last year, was favouring his back from early in his round after waiting over two hours to start on Thursday due to fog.
The 14-time major winner was two-over par through 11 holes before pulling the pin.
He has now withdrawn in three of his last eight starts.
"When we had that break. It just never loosened back up again. And when we went back out, it just got progressively tighter," Woods said.
"It's frustrating that it started shutting down like that. I was ready to go. I had a good warm-up session the first time around.
"Then we stood out here and I got cold, and everything started deactivating again. And it's frustrating that I just can't stay activated.
"It's just my glutes are shutting off. Then they don't activate and then, hence, it goes into my lower back.
"So, I tried to activate my glutes as best I could, in between, but it just they never stayed activated."
Woods bogeyed two of his first three holes and needed a miraculous chip-in for par on the other in his first round since a career-worst 82 last Friday at the Phoenix Open.
But Woods ground out five pars and two birdies in his next seven holes despite battling the injury.
Just as it appeared he may battle his way to the clubhouse, Woods double-bogeyed his 11th hole to fall to two-over and after his tee shot on the next hole he was done.
Woods had claimed to be in perfect health in the lead-up.
Share
