Tiger Woods made himself unavailable for the USA Ryder Cup team because he did not think he could win a point in the matches, the former world number one said on Tuesday (local time).
The 38-year-old American was sidelined for three months after having back surgery in March.
His form this year would have left him relying on a wildcard pick from skipper Tom Watson for next month's matches against holders Europe at Gleneagles in Scotland and he pulled out of contention last week.
"I wouldn't be ready ... and I just couldn't help the team," Woods told Britain's Sky Sports television in an interview.
"When your name is called you have to be able to go out there and get a point and I just didn't feel I could be ready enough to get a point.
"It was time to shut it down, get stronger, get more explosive again and get back for next year."
World number 11 Woods missed the cut at the PGA Championship this month, having made a late decision to play after pulling out of the WGC-Bridgestone Invitational the week before.
He is not planning to pick up his clubs for another month but will work in the gym as he builds towards a return at the World Challenge tournament in Florida in the first week of December, an event he hosts.
"We've got it all calmed down, now it's about the strengthening process," said Woods.
"I probably won't be swinging a club for another month but just getting stronger each and every day. I'm in the gym two or three times a day.
"I've got my physios, I've got my trainers there so we're working hard and then we're going to introduce dynamic training again, my explosiveness, but that's down the road, let's just get this thing stronger first."
Woods played in the Ryder Cup seven times between 1997 and 2012, missing the USA victory in 2008 after knee surgery.
Europe have won seven of the last nine editions.
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