Jordan Spieth told his caddie he could feel himself collapsing during his implosion at the Masters on Sunday.
The American's title defence at Augusta appeared on track until he found trouble on the back nine, following two bogeys with a quadruple bogey at the par-three 12th.
Spieth found water twice to put himself in trouble as he saw a five-shot lead slip away, eventually finishing three behind winner Danny Willett.
Speaking afterwards, the 22-year-old recalled a conversation with caddie Michael Greller as his round fell apart.
"At one point, I told Mike: 'Buddy, it seems like we're collapsing,'" Spieth said.
"I wanted to be brutally honest with the way I felt towards him, so that he could then respond with what is necessary to get us to rebound and he did, and we rebounded.
"I made two birdies coming in and almost made a couple more, but boy you just wonder about not only just the tee shot on 12, but why can't you just control the second shot and make five at worst and you're still tied for the lead."
A hurting Spieth had regrets after letting a potential third major, and second green jacket, slip away.
The world number two said he never took the time to compose himself after bogeys at 10 and 11.
"I knew the lead was five with nine holes to play," Spieth said.
"I knew that those two bogeys weren't going to hurt me, but I didn't take that extra deep breath and really focus on my line on 12.
"Instead, I went out and just put a quick swing on it."