Dustin Johnson surrendered a four-shot lead in his first six holes and finished the day in a four-way tie for the US Open lead as Shinnecock Hills battered the world's best golfers on Saturday.
World number one Johnson closed with a bogey at the par-four 18th in a seven-over par 77 that left him tied atop the leaderboard at three-over 213 with Daniel Berger, Tony Finau and defending champion Brooks Koepka.
Berger and Finau teed off early and stormed up the leaderboard with four-under par 66s, playing the bulk of their rounds before the sunshine and sea breezes dried out the course.
By the time the leaders teed off, Shinnecock's greens were hard and fast, and players could only watch as good approach shots rolled off the domed putting surfaces and the most lightly hit putts skated past the holes.
The sight raised the spectre of the 2004 US Open at Shinnecock, when weekend wind dried the course, rendering some of the greens virtually unplayable by Sunday.
"Frankly, we missed it with the wind," admitted US Golf Association chief executive Mike Davis. "The speed of the greens was too much for the wind we had. It was a very tough test, but probably too tough this afternoon."
Johnson, four-under and leading by four heading into the round, was in trouble early with his first double bogey of the week at the par three second. His four bogeys on the front nine included three in a row at six, seven and eight.
As he struggled, England's Justin Rose and Sweden's Henrik Stenson tussled for the lead.
But Rose had three bogeys in a row at eight, nine and 10 and bogeyed two of his last three to come in with a 73 that left him alone in fifth on 214.
Stenson capped his four-over 74 with a bogey at 18 and was alone in sixth on 215.
Despite all the difficulties, Johnson arrived at the 18th tee with a one-stroke lead. His approach from the fairway bounced near the pin and rolled 17 feet past. His first putt roared eight feet past, and his par attempt coming back burned the edge but didn't drop.
Koepka, who had two birdies and four bogeys in his two-over 72, voiced concern that the golf course would hold up through the final round.
"I hope these greens are good enough to play tomorrow," said Koepka, who lifted the trophy at Erin Hills last year with a record-equalling 16-under par total.
"They're very borderline right now to be honest with you."
Berger had seen the danger in the latter stages of his round.
Berger rolled in birdie putts of 30 feet, 23 feet and 26 feet, finishing with six birdies and flirting with a 65 that would have been the best ever US Open round at Shinnecock.
But Berger said pin placements near the borders of the sloping greens were particularly challenging.
"You hit one by, three feet past the hole and it's going 40 yards away from the green," he said.
"I hit plenty of really good shots in there. I hit one on the par five, number five, that I landed 10 feet from the hole, and it ended up 50 yards away. So that's just how it is out here."
- Mickelson madness? -
That may have been what led to Phil Mickelson's astonishing performance at the 13th green -- where after watching his bogey putt roll past the cup and head down a hill he ran over and batted the still moving ball back toward the hole.
With the two-stroke penalty Mickelson took a sextuple bogey 10.
Playing partner Andrew Johnston called it a "moment of madness" but Mickelson, a five-time major champion, insisted it wasn't just a display of petulance.
Instead, he said, he decided the two-stroke penalty he knew he would receive would be preferable to letting the ball escape off the green.
"Look, I don't mean disrespect to anybody," he said. "I know it's a two-shot penalty. At that time, I just didn't feel like going back and forth and hitting the same shot over.
"It's meant to take advantage of the rules as best as you can," he said.