Maybe Phil Mickelson got too much rest, or maybe the course got too hard.
Mickelson had a much better run at Merion Golf Club when he jetted in at 4 a.m. on Thursday and shot a three-under-par 67 on two hours sleep.
The second round featured Mickelson frittering away his first-round lead and then, on the difficult par-four finishing hole, making his only birdie of the day to reclaim a share of the lead.
It was so Phil-like. His finishing birdie was only the ninth on No. 18 in two days. It is the toughest hole on course playing to average of 4.7 strokes.
With second-round play halted because of darkness, Mickelson got into the clubhouse with a second-round 72 to join Billy Horschel as co-leaders at one-under 139 through 36 holes.
Sixty-eight golfers out of 156 have yet to complete their second rounds.
Horschel and Mickelson lead a pack of what seems like dozens who could still win the 113th U.S. Open.
Horschel shot three-under 67 earlier in the day and looked like he would be the solo eader Friday until Mickelson sank his putt in a setting sun.
Among those one-shot back at even par include Luke Donald, Steve Stricker, Justin Rose, Ian Poulter and 21-year--old amateur Cheng-Tsung Pan, playing not for a sponsor but in the colors of his school: the University of Washington.
Nineteen players, including Tiger Woods, are only four shots back at three over. Woods bounced back from his three-over 73 in the opening round with an even-par 70 to find himself in contention for his 15th major, but first since the 2008 U.S. Open at Torrey Pines.
Horschel played a brilliant round on a torturous course, hitting all 18 greens in regulation.
"It was a great day," said Horschel, who played college golf at Florida. "Four birdies at a U.S. Open, I'll take it."
He should take it and run.
Merion has proven to be a beast of a set-up after predictions that wet weather and soft conditions would turn the championship into a dart board.
ESPN Stats & Info reported at one point late Friday that the field was a collective 1,286 over par. The wicker-basket pins weren't very accessible and it showed all day on scorecards and players' faces.
Merion is not very long at 6,901 yards but the second round played to an average of five over 75.
Phil Mickelson has back-to-back bogeys to lose the lead | 4:21 p.m.
It had been looking like Phil Mickelson's U.S. Open to lose and, as we all know, he's lost plenty of them.
Mickelson has yet to record a second-round birdie at Merion Golf Club and is starting to leak ball-cleaner water. He has fallen out of the lead and to even par after a disastrous three-putt bogey at the par-four 12th hole and a bogey at the par-three No. 13.
Steve Stricker birdied No. 13 to join Billy Horschel (in the clubhouse) and Justin Rose (on the course) as leaders at one under.