Woods says he can't play in Ryder Cup
Woods said on his website Wednesday that he's been told by doctors the muscles in his back "need to be rehabilitated and healed" and that he should not play or practice golf.
He said he plans to return to competition in December at his World Challenge event in Orlando, Florida.
Watson had not ruled out taking Woods as one of his captain's picks for next month's matches in Scotland.
"I have already spoken to Tom about the Ryder Cup, and while I greatly appreciate his thinking about me for a possible captain's pick, I took myself out of consideration," Woods said.
"The U.S. team and the Ryder Cup mean too much to me not to be able to give it my best. I'll be cheering for the U.S. team. I think we have an outstanding squad going into the matches."
Woods, 38, missed the cut at last week's PGA Championship by five shots. He played despite pulling out of the WGC-Bridgestone Invitational the week before after wrenching his back on a swing and suffering back spasms.
His recent injury isn't related to the back surgery he had in March to fix a pinched nerve, which kept him out of competition for almost three months.
Woods was named the PGA Tour's Player of the Year last season after winning five times but didn't finish higher than 25th in any of his eight worldwide starts this season and was nowhere near qualifying for an automatic spot on the U.S. team.
He has played in seven of the last eight Ryder Cups, only sitting out in 2008 after having knee surgery.