Tiger Woods withdrew from the Dubai Desert Classic on Friday with back spasms after shooting an opening-round 77 a day earlier.
Woods' manager, Mark Steinberg, said Woods suffered from spasms on Thursday night after dinner.
"Tiger Woods went into a spasm in his lower back fairly late last night ... got treatment done early this morning for 3 1-2 hours, but can't get it out."
"He says it's not the nerve, but back spasm, and he can't get the spasms to calm down. He can move around, but he can't make a full rotation in his swing."
Woods made a comeback after multiple back surgeries after a 16-month layoff, and was expected to play four times in five weeks, starting from last week's Farmers Insurance Open in Torrey Pines, where he missed the cut.
The European Tour, without giving a reason, announced his withdrawal on Friday before Woods began his second round at Dubai.
After Woods' opening round, he said "I wasn't in pain at all ... I was just trying to hit shots and I wasn't doing a very good job."