Martin Kaymer lines up a putt on the 14th green during the first round at Pinehurst No. 2. (Streeter Lecka/Getty Images)

All the clowns climbed into the Volkswagen on Thursday afternoon at Pinehurst No. 2. Keegan Bradley wedged up against Jason Dufner, good buddies who have also won major championships. Graeme McDowell piled in with his grinding game, the style that brought him a U.S. Open title four years ago. Dustin Johnson, Jordan Spieth, Matt Kuchar — stars seeking their first major titles — crammed in, too, hovering around the lead. Someone needed to toss open the door and burst out.

Just after 6 p.m., with the light growing low across this rough-and-tumble course, Martin Kaymer did exactly that. He took a mess of a day — when, for the better part of 12 hours, no leader board was large enough to contain all the contenders — and brought both clarity and class. The German made three birdies over his final five holes and finished with a steely par putt at the last, good for a 5-under 65 that showed every one of his skills and separated him from all the characters in that Volkswagen by three shots.

“I’m not freaking out about it,” Kaymer said. But he acknowledged it as “exceptional,” and that it was, because Pinehurst has never yielded a score that low in the three U.S. Opens staged here.

The reason Kaymer can be zen about such a performance? He has been to the top and experienced both the perks and the drags that come with it. He won the PGA Championship in 2010, a result that helped push him to the No. 1 spot in the Official World Golf Rankings. At 29, he has already holed the clinching putt at the Ryder Cup, and in May he added the Players Championship to a burgeoning résumé.

In a way, though, he needed that victory at the Players. He had taken to scanning articles and social media about himself, commentary wondering if he would ever repeat the promise he showed at 25. And here’s something an athlete doesn’t often admit: It got to him.

“You can’t avoid listening to it or reading it,” Kaymer said. “The outside, they put a lot of pressure on you. And at the end of the day, it’s up to yourself if you let it get to you or not. But you have to be very, very strong to really [not] care. I care about it.”

No one else in the 156-player field, though, would begrudge Kaymer any of his accomplishments — not in the past, not in his sublime round Thursday.

“It was an impressive round,” said Bradley, who played alongside Kaymer. “One of the best rounds I’ve seen, for sure.”

Kaymer was able to pull it off because the victory at the Players relieved him of the burden of thinking about technique, and allowed him to just play. That wasn’t as easy this spring, when he had fallen to 63rd in the world. But it was part of the process. Success changed him — or at least what surrounded him — and he had to learn to deal with that.

“You learn a lot about yourself and that makes you more mature, and it takes some time getting used to that change,” Kaymer said. “You change all the time, obviously, but that change is quite dramatic. It takes a lot more time than you thought.”

Part of that evolution, then, is understanding what Thursday meant in the larger picture. In two words: very little. The Open has barely begun. Four players tied with 2-under 68s — Kevin Na of Las Vegas, Brendon de Jonge of Zimbabwe, McDowell of Northern Ireland and 49-year-old qualifier Fran Quinn of Massachusetts.

The group of 10 players at 1 under includes all manner of accomplishments — FedEx Cup champ Henrik Stenson, who’s ranked second in the world; Kuchar, among those in the discussion for best player without a major title; Spieth, the 20-year-old Texan who played in the final group at both the Masters and the Players; Johnson, who led going into the final round of the 2010 Open at Pebble Beach and who lost the PGA Championship later that summer to Kaymer; and Bradley, who won the 2011 PGA.

Those players and others are obviously still in it. But Kaymer’s round altered the feel of the tournament for so many. Phil Mickelson, six times a runner-up in this event, shot an even-par 70 in the morning. Rory McIlroy, the 2011 champ, went out early and shot a 71 that might have been better. But when they walked off the course, neither was upset because the lead at the time was 2 under. It didn’t figure to go lower.

“Fairly content,” McIlroy said.

Indeed, Kaymer was asked Wednesday what score he thought would win. His response: 8 over par. The course was that firm already, and the tournament hadn’t yet started.

“This golf course is difficult and good shots are going to finish in bad spots, and you’ve just got to really, really grind hard,” McDowell said after his morning 68. “It’s not going to give you a lot of opportunities. . . . You aren’t going to make 20 birdies out here [all week]. It’s as simple as that.”

Yet after his six birdies, Kaymer is well ahead of that pace, in part because the U.S. Golf Association watered the greens before play began, making them considerably more receptive.

“I thought it was very playable,” Kaymer said.

That, by day’s end, seemed obvious. But this is neither the Masters nor the Greater Milwaukee Open, and no one — least of all Kaymer — thinks four 65s is remotely possible. Thursday, then, was Thursday, a day Kaymer could assess the hodgepodge of players on the leader board, his own accomplishments and struggles — and separate himself from it all.