Phil Mickelson trails by 13 shots

PINEHURST, N.C. -- A dejected Phil Mickelson all but conceded his chance of winning a first U.S. Open was over after a 3-over-par 73 left him 13 strokes back of tournament leader Martin Kaymer on Friday.

The culprit again was his putting, as Mickelson 3-putted on four occasions and took 34 for the round.

"I feel like I'm playing well enough to win the U.S. Open, except for putting,'' said Mickelson, who is tied for 33rd. "It's kind of the same story. After I've 3-putted three or four times, I kind of lose my focus on the other stuff. It affects my ability to concentrate and my momentum and energy.

"It's a frustrating time because I feel like the other parts of my game are there. I had such a great stretch last year putting. I feel like it's in there. It doesn't feel like the ball is coming off bad. I don't feel like the stroke is bad, but I'm just not dialed in. I'm just not making them.''

Mickelson reverted to his conventional putting stroke at the start of the second round, thinking he had turned the corner during practice. And birdies at the second and third holes got him to 2 under for the tournament and -- while still eight strokes back of Kaymer -- in a tie for second.

But Mickelson didn't make another birdie, instead adding five bogeys.

"I made the putt on 2 and 3, and I hit a really good putt on 5 that didn't go, and I thought I was going to have a good day,'' Mickelson said. "The 3-putt on 6 shook me a little bit. Then 8. After that I was really fighting it.''

Mickelson came into the tournament without a top-10 finish this year on the PGA Tour but encouraged by the setup at Pinehurst No. 2 and hopeful he could get his game turned around.

A victory at Pinehurst would make him just the sixth player to win a career Grand Slam -- victories in all four major championships.

"I'm not overly optimistic,'' Mickelson said. "Obviously I'm not in good position. You can't fire at a lot of the pins. You've got to make 25-, 30-footers, and I'm just not doing it. I'm not going to give up, you never know. I've had rounds that kind of clicked, like at Charlotte [a third-round 63], where all of a sudden the putter clicked and I just saw the line, but the ball started going in and went on a run.

"And tomorrow I need to shoot 6- or 7-under par to have a realistic chance.''

Mickelson has a record six runner-up finishes at the U.S. Open, the first coming here in 1999 and the last at Merion in 2013. Given Kaymer's huge advantage, it appears second might be the best he can do.