Phil Mickelson came to Pinehurst as the U.S. Open’s undisputed best story, a six-time runner-up in golf’s national championship who finished second here in 1999.

The problem with him remaining a story: his iffy putting stroke, which he has battled all year. And that’s exactly what makes him an also-ran headed into the weekend. Mickelson shot a 3-over-par 73 in Friday’s second round that featured three three-putts and left him 3 over for the tournament, 13 back of Martin Kaymer’s lead.

“I feel like I’m playing well enough to win the U.S. Open,” Mickelson said. “Except for putting.”

There is some truth in that assessment because Mickelson has confidently struck his driver for the better part of two days, and when he birdied both Nos. 2 and 3 Friday he was 2 under for the event. But he failed to birdie the par-5 fifth, then three-putted the par-3 sixth — his first gaffe.

And he admitted that when that happens, his mind wanders. His next three-putt came just two holes later.

“After I’ve three-putted three or four times, I kind of lose my focus,” Mickelson said. “It really affects my ability to concentrate and my momentum and energy.”

Mickelson had committed to a “claw” putting grip for Thursday’s first round, but he changed back to his conventional grip for Friday.

“I thought I was going to have a good putting day,” he said. But his 34 putts were almost four more than the field averaged.

Mahan’s major mistake

Hunter Mahan’s scorecard showed him with a second-round 72, which gave him a two-day total of 6-over 146 — outside the cut line by a single shot. But that doesn’t begin to tell the story of his Friday.

At the 18th hole — his ninth of the day — Mahan struck a drive to what he thought was the left-center of the fairway. John Wood, his caddie, walked out to the ball first and reported the yardage to his player. Mahan then rapped his second shot onto the green.

But at the green, Mahan and Wood realized they had played the ball of Jamie Donaldson, the Englishman in their group. Donaldson, afterward, had in turn played Mahan’s ball.

“It was one of those things I couldn’t explain to you,” Mahan said. “Off the tee, it looked like that’s where my ball should have been.”

Mahan and Donaldson were assessed two-stroke penalties and had to report back to the fairway and play from their original spots.

“You can’t imagine yourself doing something colossally as stupid as that,” Wood said. . . .

In 2012, when he first won the Masters, Bubba Watson missed the U.S. Open cut at the Olympic Club in San Francisco. He won his second Masters in April — and missed the cut here, following his opening 76 with a 70 to miss by a shot. . . .

Leesburg native Billy Hurley III, a Naval Academy grad who lives in Annapolis, made four bogeys over his final six holes to shoot 74 on Friday but made the cut on the number, finishing at 5 over and advancing to the weekend of his first major championship.