SOUTHAMPTON, N.Y. — Whether he ever wins a U.S. Open — and that prospect is increasingly bleak at age 48 — Phil Mickelson will be remembered for what happened on the 13th green at Shinnecock Hills on Saturday.

Call it the Mickelson Meltdown.

His bogey putt from above the hole ran by the cup and was headed down a slope when he ran over and swatted it back toward the hole as the ball was still moving.

“Sometimes it gets a little goofy, sure,” he said, “but it’s all within the rules.”

Mickelson’s shocking display in the third round earned him a 2-stroke penalty for breaking the rule against hitting a moving ball and led to a 10 on the hole, an 81 overall. He went from shooting a 69 to making the cut to falling apart so badly that playing partner Andrew Johnston called it “a moment of madness.”

“I’ve had multiple times where I’ve wanted to do that,” Mickelson said, explaining he preferred the 2-stroke penalty to having to play the ball from off the green. “I just finally did.”

Saturday was Mickelson’s 48th birthday, and there were good vibes everywhere early in his round. He was serenaded with “Happy Birthday” at nearly every green, and even after four consecutive bogeys the fans were supportive.

“People here have been awesome, they made my birthday special,” he said.

Then came No. 13, where nothing was special — just outrageous.

Mickelson jogged after the ball after it curled around the hole, realizing it was about to head down the other side of the green. His swat sent the ball off the hole.

He then two-putted. With the 2-shot penalty, he was given a sextuple-bogey 10 that was the highest score on any hole at this U.S. Open, according to the USGA.

“I’ve wanted to do that many times. I should have done it several times at Augusta on 15,” he said.

As he walked off the green, he could be seen smiling and talking to Johnston, who also was smiling.

“I said, ‘That is one of the strangest things I have ever seen’ and started laughing, and said ‘sorry’ about laughing,” said Johnston, a jovial Englishman with the nickname Beef. “He just laughed at me, he had no words to say. We just laughed.

“It’s something you might see at your club with your mates. It was strange, no one ever has those thoughts, it just happens.”

Mickelson’s actions were reminiscent of John Daly hitting a moving ball at Pinehurst No. 2 in the 1999 U.S. Open. Daly was on No. 8 in the final round when he took an 11 on the hole and signed for an 81. He then said: “This is my last U.S. Open — ever. I’ve had it with the USGA and the way they run their tournaments.”