Within two troublesome holes, Rory McIlroy (inset) had gone from joint leader to also-ran.
All had looked like it was going to plan when the world number one added three pars to his opening birdie to remain alongside eventual winner Adam Scott at the top of the Genesis Invitational leaderboard after four holes of the final round.
But he ran up a triple-bogey seven on the fifth on his way to a disappointing 73 to finish joint fifth in his first week as world number one since September 2015.
That Scott made a similar error and ended with a six was scant consolation, especially after the two-shot swing at the sixth left McIlroy trailing by three.
As McIlroy was keen to point out, he played the other 17 holes in one under for the day, a score that would have left him tied at the top but for his difficulties on the fifth.
"They set the course up a little tougher today than it has been the last few days," McIlroy said. "Factoring in that it's a little firmer than it has been and just with how the weather's been and a little bit of wind and all of a sudden it becomes a very tricky golf course.
"It was definitely the toughest day of the week. The wind was up, hole locations were sort of tricky spots but I didn't expect it to be as difficult as it was."