The American world number one struggled to a stunning seven-over-par 77 in Sunday's final round at Firestone Country Club, his highest final score as a professional, to lie joint second-last in the 80-strong field.
At a venue where he has previously reigned supreme with seven victories in 11 starts, Woods carded two double-bogeys in the last five holes to post an 18-over total of 298.
It was his highest 72-hole aggregate on the PGA Tour, his worst relative to par and the first time since the 2003 PGA Championship he had strung together four rounds over par.
"(I'm) just not playing well," a grim-faced Woods told reporters after completing his round nearly three hours before the leaders were scheduled to tee off.
"Shooting 18 over par is not fun. The only thing I can say all week is I was patient, and unfortunately that's not enough."
Asked if he could recall a similar struggle with his game, he replied: "Absolutely. I went through something like this when I changed my swing in '98 and '99, second half of '97.
"When I kind of tore my swing apart with (coach) Butch (Harmon) basically after the Masters in '97, it took me two years to get it back before I started playing well."
Perhaps the most remarkable comment made by Woods following his dismal Firestone display was that he had not been shocked by his on-course struggles.
UNRAVELLING MARRIAGE
"No, it doesn't surprise me at all actually," the 14-times major champion said before hinting at the impact of his unraveling marriage to his Swedish wife Elin. "It's been a long year."
Asked if his golfing struggles this week had been mainly mental, he again replied stone-faced: "It's been a long year."
Woods, who has lost the aura of invincibility he once enjoyed since his double life was exposed at the end of last year amid revelations of serial philandering, played with compatriot Anthony Kim in the final round at Firestone.
"He's obviously struggling," Kim said after carding a 76 to finish two shots better than Woods. "He's not hitting it very well and he's just not the regular Tiger we're used to seeing.
"He's obviously had a lot of stuff going on and he's dealing with that. That's more important than golf because I think golf is an easy thing to do once your personal life is straightened out. I'm sure it's going to happen soon for him."
Woods is not yet an automatic selection for the October 1-3 Ryder Cup at Celtic Manor in Wales and said he had no desire to take part in the biennial competition based on current form.
"Not playing like this, definitely not playing like this," he added. "I wouldn't help the team if I'm playing like this. No one would help the team if they're shooting 18 over par."
Asked if he would pick himself if he was the U.S. Ryder Cup captain, Woods replied: "I think I can turn it around but we've got a lot of time between now and then, which is good."
He lies ninth in the U.S. Cup standings with the top eight automatically qualifying after next week's PGA Championship.
Woods has yet to win this season after eight starts on the PGA Tour and will be seeking a 15th major title, and his fifth PGA Championship crown, at Whistling Straits next week.