But world No.6 Woods is optimistic about completing the no-cut BMW Championship starting Thursday.
He was impressive in the first nine of his Wednesday pro-am, shooting an unofficial four-under-par 32.
But Woods did not hit a full shot after his drive on the 10th hole.
The 43-year-old, who underwent spinal fusion surgery in 2017, only chipped and putted for the back nine.
Afterwards, Woods insisted he was healthier than last week and was eager to play the Chicago course where he won the 1999 and 2006 US PGA Championships.
“Way, way better,” Woods said of his back.
“It was nice to take those days off [last week] and let it calm down and get a bunch of treatment on it.
“It feels so much better. I played the front nine today and played quite well; it was nice to see.”
Woods won the Masters in April for his 15th major and fifth title at Augusta National, but he has played just five tournaments since then.
He missed the cut at the US PGA Championship and British Open, while last week’s withdrawal was the first time he has pulled out during an event worldwide in two years.
In an ominous admission, Woods said making swing changes to compensate for his plagued back was diverting the injuries to other areas of the body.
“The forces have got to go somewhere, and unfortunately when I make any kind of tweaks and changes to my swing, it’s like a new body part is aching,” he said.
“Unfortunately I can’t play around [my] back like I used to, and unfortunately things flare up.
“I’ve tried to make [swing] tweaks all year, trying to ease the stress off my back while I was still playing.
“Unfortunately I haven’t really done a very good job of that, and when I have, I’ve hit the ball quite well.”
Woods is 38th on the FedEx Cup points standings and will need at least a solo 11th place to climb into the top 30 who qualify for next week’s Tour Championship play-offs finale.
Woods won that event last year, at East Lake Golf Club in Atlanta.