ERIN, Wis. — The biggest surprise at this U.S. Open was not who was leading, but who was leaving.

While Dustin Johnson, Rory McIlroy and Jason Day – the top three players in the world – all missed the cut, they left behind the biggest 36-hole logjam in 43 years at the U.S. Open.

Paul Casey chopped his way to a triple bogey, only to respond with five straight birdies that carried him to a 1-under 71 and make him the first to post at 7-under 137. He set the target early under warm sunshine, and even as the wind tapered in the afternoon, no one could pass him.

Brooks Koepka had the lead until he turned a birdie chance into a bogey on the par-5 first hole after making the turn. He didn’t make a birdie the rest of the way and had to settle for a 70. They were joined at 7 under by Brian Harman and Tommy Fleetwood, who each had a 70.

Right behind was a trio of players that included Rickie Fowler, who went 28 holes before making his first bogey and then went three holes without making a par. Fowler shot a 73 and was still very much in the hunt at a second straight major.

The four-way tie was the largest after two rounds in a U.S. Open since Winged Foot in 1974, when the names were more familiar for a major – Raymond Floyd, Arnold Palmer, Gary Player and Hale Irwin, who went on to win his first major.

The last six majors have been won by first-time major champions, and that cycle has a good chance to continue. The top 18 players on the leaderboard going into the weekend have combined for zero majors. Only a half-dozen of them have even experienced Sunday contention in golf’s biggest events.

“Tomorrow will be a very cool experience,” Fleetwood said. “It’s still Saturday – 36 holes is a very long time in a U.S. Open. Anything can happen.”

Just about everything already has at Erin Hills.

A commercial blimp crashed and caught fire just outside the course Thursday, about the time the county health department was analyzing samples that confirmed evidence of the E. coli bacteria in water at a hydration station near the 12th hole. The USGA is providing complimentary bottled water the rest of the week. There have been no reports of anyone getting sick.

Then Friday, a 94-year-old man stopped breathing while in a grandstand on the sixth hole and died of what Washington County officials said appeared to be natural causes.

Next up is a weekend without most of the biggest names in golf.

Of the top 12 players in the world rankings, the only ones still in the tournament are Fowler, Hideki Matsuyama (-5), Sergio Garcia (-3) and Jordan Spieth (even par).

Fowler has the best chance, even though he lost so much ground over the final two hours. He went from pouring putts into the center of the cup to burning the edges, and his 39 on the back nine cost him the lead, though not his chances of breaking through for that first major.

“We’re in a good spot,” Fowler said. “Looking forward to the next two days.”

Casey discovered how little it takes to make a big number in the U.S. Open.

He laid up in the rough on the 14th hole, took two chops to get out of more rough behind the green, and staggered away with a triple-bogey 8 that might have ruined his day. Moments later, he began a run of five straight birdies that put him right where he wanted to be going into the weekend.

“Not every day you enjoy a round of golf with an 8 on the card, but I’m a pretty happy man,” Casey said. “Yeah, it was a bit of a roller coaster. I guess it’s rare you get through a U.S. Open or any major without some kind of a hiccup.”