"I needed something," Kaymer said. "A win, whether it was the Players or a regular PGA Tour event. For my confidence, that all the work I put in the last couple of years was worth it. It was huge. It made a difference, to show me it was all good. When you come to a big tournament, it's nice if you've [just] won before.
"I didn't make many mistakes. Finally, I made some putts at the end. It was a nice way to finish. I'm very happy."
Kaymer closed with a 31 on the back nine, including birdies on three of the final five holes. And he made a delicate 5-footer to save par at 18.
"Three or four of my [six] birdies were very short putts, that you should make," said Kaymer, whose lone bogey came at the seventh. "It's obviously an excellent score. [But] it's only the first one. Usually, the golf course only gets more difficult. It's very nice to lead right now. I was very surprised the golf course played fairly soft. It was very firm Monday, Tuesday and Wednesday. They must have changed something.
"I got asked [on Wednesday] what score I would take for the whole week and I said 8-over. So hopefully that's not going to happen. I'd be disappointed. [But] nobody should expect 5-under the next three. I don't. Tomorrow will be a different day with different conditions. It's a tough golf course. I just played well. I had a very good day."
Fourteen others are also in red numbers, with 20 more at even. Among the four at 68 is 2010 champ Graeme McDowell, who missed the cut last June at Merion after losing by one to Webb Simpson the year before at Olympic. He's tied with Kevin Na, who lost in a playoff 2 weeks ago at The Memorial, Brendon DeJonge, who's never won on the PGA Tour and is playing in his second Open, and 49-year-old Fran Quinn, who played in the last of his three Opens 18 years ago.
"I really kind of felt like I got my head in the right place," said McDowell, who had one eagle (at the par-5 fifth), a birdie and a bogey. "You've just got to really, really grind hard. The golf course isn't going to give you a lot of opportunities. It tempts you into making mistakes. I played very conservatively. Generally kept the ball exactly where I wanted to.
"You aren't going to make 20 birdies out here, it's as simple as that. The winner of this tournament is going to make 10 to 12, maximum. That's only three a round. That's what I mean by preparing yourself mentally for the fact that you're just not going to get a pat on the back very often."
The scrum at 69 is composed of Brandt Snedeker, world No. 2 Henrik Stenson, Matt Kuchar, Jordan Spieth, Brendon Todd (who's making his Open debut), Hideki Matsuyama (who just won The Memorial), Dustin Johnson, Harris English, 2011 PGA champ Keegan Bradley and Francesco Molinari, whose brother Eduardo won the 2005 U.S. Amateur at Merion.
Johnson would have been in the 3-hole playoff with Kaymer and Bubba Watson at the 2010 PGA if he hadn't grounded his club in the sand on the final hole and taken a penalty.
Among those at 70 are six-time runner-up and reigning British Open champ Phil Mickelson, 2012 Masters champ Charl Schwartzel, Ian Poulter, Steve Stricker, Paul Casey and Rickie Fowler, who wore knickers to honor the memory of 1999 Pinehurst champ Payne Stewart, who died 4 months later in a plane crash.
"Everyone knows how difficult it is to keep that momentum going in a U.S. Open," said Kaymer, who sank the winning putt for Europe in their final-day comeback Ryder Cup win at Medinah 20 years ago. "You will make a couple of bogeys out there. It's about playing the next hole. You can't really think too much about the positives, or two much about the negatives, because it's too much to think about."
Kaymer was one of the many guys in this goofy game who tasted early success and then for whatever reasons went through a down period. He's hoping that's mostly, finally behind him.
"There are things that come with it," he reflected. "You learn a lot about yourself. It takes some time to get used to that change. You change all the time, and that can be quite dramatic. It takes a lot more time that you thought. You have to be really, really strong. Winning The Players was a big relief.
"The pressure from the [outside], which was kind of annoying sometimes, because you can't avoid listening to it or reading it. By the end of the day, it's obviously up to yourself, if you let it get to you or not. You have to be very strong to really don't care. I care. Therefore, it was quite nice to get that out of here, the pressure and all the negativity. That obviously helps you as a person, but more as a player . . .
" 'Is he ever going to come back? Is he a one-hit wonder?' You know, those things. I understand why people think like this. It's quite normal. Deep inside, I never doubted anything or what I'm doing. At the same time, it was quite funny, because I knew that it's just crap. I was very secure about myself. So I was very fortunate to experience the highs and lows. I'm sure there are going to be other lows in my career at one stage, but I can accept it better."
Especially if his resumé has another defining notch in it come Sunday evening.
On Twitter: @mikekerndn