Woods, an eight-time winner of the Bridgestone at Firestone Country Club in Akron, said his three-over 73 had nothing to do with any injury or illness.
"I just played like crap," said the 14-time major champion, who started the day tied for 10th and five shots off the lead and finished 11 off the pace.
"I didn't warm up very well. I didn't hit the ball crisp or clean," Woods said.
The lackluster effort was bound to draw questions about his fitness.
Since winning his most recent title at the 2013 Bridgestone, Woods has battled back trouble that led to spinal fusion surgery in April of 2017.
As recently as last September he wasn't sure if he'd return to competitive golf, but his comeback has steadily gained steam to see him rose from outside the top 500 in the world rankings at the start of the year to 50th.
"He wasn't hitting it as far as he normally does," said Australian Marc Leishman, who played alongside Woods. "His good stuff, it's still good. He's right there. He might have had an off day. We all do. I wouldn't put it down to anything more than that."
Woods's effort ended a run of 10 rounds at par or better, dating back to the Quicken Loans National in July where he tied for fourth.
He hit just seven of 14 fairways and only nine of 18 greens in regulation as he finished with four bogeys and one birdie.
"I hit some good shots today, but also I didn't feel like I was in control of the golf ball today," Woods said. "And then I had some putts where, you know, I had some good looks at it to turn it around, build some momentum, I didn't make anything.
"I just feel like I really couldn't turn it around today, just felt off. I had a little bit of a pull, a little bit of a block, a little here, a little there. Just wasn't as sharp as I needed to be, especially with everyone making a bunch of birdies.
"I needed to go get it today and I didn't do it."