'It's not fun when it goes this way,' he said.
Mickelson, trying to become the first player since 1990 to win back-to-back titles at Pebble Beach, instead missed the cut for only the third time in his career with a 78 that wasn't nearly as bad as it looked on paper.
He putted for birdie 16 times and made only one of them, an 18-inch putt on the fourth.
His tournament ended on the par-5 14th with an aggressive play, a couple of bad swings, a bad break and a very big number.
Mickelson tried to cut the corner on the 585-yard 14th by playing right of the bunker at the dogleg. From a decent lie in the rough, he decided to hit a hybrid to just short of the green, which would leave him a pitch shot with his 64-degree wedge.
But the hybrid didn't work out -- twice.
'It ended up shooting right on me and went out of bounds,' Mickelson said. 'And then I did it again.'
He finally opted to hit 5-iron to the fairway for his sixth shot, then his wedge spun off the green, down the slope and into a muddy, sloppy lie under a tree. His eighth shot made it halfway up the hill, he chipped that on to 15 feet and two-putted for an 11.
Mickelson's caddie could not think of a higher score on any one hole in his career, and PGA TOUR officials were scanning through scorecards to verify. He has shot some high scores with some questionable decisions during his career, but rarely has Mickelson looked more capable of winning and wound up checking out so early.
He finished his round by taking an aggressive line off the 18th tee, but it went left and into the surf crashing below the fairway. That gave him a 78, which wasn't his worst score at one of his favorite courses. Mickelson closed with an 80 five years ago at Pebble Beach.
'It's disappointing, but I'll be back,' Mickelson said. 'I've got to get this putter worked out. If I had made anything, I wouldn't have had to force it.'
Mickelson was coming off a playoff loss in the FBR Open outside Phoenix. He will play next week at Riviera in the Northern Trust Open, then wrap up his five straight weeks on the West Coast at the Accenture Match Play Championship.
That's the kind of event where an 11 only costs a player one hole, not a tournament.