Tiger Woods blamed late season fatigue for his dramatic collapse over the closing stretch at the Tour Championship on Friday after he had surged into contention with five birdies in his first 13 holes.
The American world number one, FedExCup points leader coming into this week and the title favorite at the PGA Tour's season-ending event, ended up with a one-over-par 71 on a sun-splashed day at East Lake.
Woods, seeking his sixth victory this year but nine strokes off the pace overnight, ran up a double-bogey at the 14th, a bogey at the 16th and an ugly triple at the 17th as he finished well down the leaderboard at four-over 144.
"I put everything I had into that start and didn't have much at the end," Woods, who had declined to speak to reporters the previous day after opening with a 73, said of his round.
"Just ran out of gas. I'm tired."
Asked whether he had suffered from physical fatigue, the 14-times major champion, who prides himself on his fitness and workout regimen, replied: "Yeah, definitely."
Woods, who had experienced some back trouble during The Barclays, the first of the four FedExCup playoff events, was then asked if his back was okay.
"It's been just a long, long grind," the 37-year-old American replied. "Everyone out here has got some knick-knack injuries, and guys are taped up and banged up a little bit. We have played a lot of golf from the British Open on."
However, Woods was predictably optimistic when asked to assess his overall position going into the final two rounds at East Lake where an elite field of 30 players is competing.
"I'm still in contention," he said. "There's 36 holes. That's why we play. That's why we play four rounds.
"This is not a sprint. It's tournament golf. It's four rounds. It's a marathon. You've got to keep plugging around."
Frustrated after failing to make a single birdie in his opening round at East Lake, Woods grazed the edge of the cup with his first two birdie attempts from mid-range in the second round.
He finally ended a run of 20 holes without a birdie when he drained a 10-footer at the par-four third, raising both arms skywards in mock celebration before blowing a kiss to the crowd.
"The funny thing is I thought I missed it high, and then the grain just absolutely smoked it at the end, and I almost missed it low," Woods grinned. "Ended up going in.
"It was finally nice to make a birdie in, what was that? 21 holes?"
Woods, FedExCup champion in 2007 and 2009, gained further momentum with two more birdies, sinking a four-footer at the eighth and two-putting at the par-five ninth to reach the turn in three-under 32.
Second-last overnight in the elite field, the world number one briefly moved into the top 10 after picking up further shots at the 12th, knocking in a four-footer, and at the 13th, where he rolled in a 15-footer, to get to five under for the day.
Woods' round then unraveled in spectacular fashion.
He double-bogeyed the 14th after hitting his tee shot way left, staying in the left rough with his second, then dumping his third into a greenside bunker from where he failed to get up and down.
Woods went on to bogey the 16th after finding the right rough off the tee and failing to reach the green in two, then butchered the 17th after his tee shot sailed well left into water to card a triple-bogey.
"My legs were just tired," Woods said of his tee shot at the 17th. "I didn't rotate through the ball, and I turned it over. Same thing I did over on 14. Same shot."
(Reporting by Mark Lamport-Stokes; Editing by Frank Pingue)