Beyond the cool customer you see on TV is a fierce competitor, tireless worker, and a golf nut who just wants to go play—even after giving away a major. Here's the DJ you don't know, from some who know him best.
College coach, director of coaching at Dustin Johnson Golf School
[At a tournament] during his sophomore year, he double-bogeyed the first hole, so he's 2-over. Then we had a weather delay. He comes out [after] and eagles the next hole, then birdies the next five and wins his first event. That's the kind of competitor he is.
Vice president at TaylorMade
When DJ first came to TaylorMade headquarters [in 2007], I set us up with a round of golf with Phil [Mickelson]. On the fifth hole, into the wind, Phil and I hit a good one, and Dustin hits his about 18 yards farther. DJ shoots 31 on the front and is 1-up on Phil. This college kid was not at all intimidated playing with a superstar. He just didn't care. Phil shot, like, 30 on the back, for a 62, and DJ shot 64. In the car going home, DJ was so pissed that he lost. I went back to TaylorMade saying, "He's going to be an amazing player."
He goes, "Joey D., I want to do whatever it takes to win a major and be No. 1 in the world." Now, if I had a dollar for every Tour pro who told me that… [But] when he said it, he meant it. He worked out every day for three straight months. He did two-a-days. He was up early, eating right. He asked the right questions. He's a true athlete, and when an athlete with his talent level really works at it, it's a whole new game.
The Monday after Chambers Bay, Wayne [Gretzky], myself and a couple of buddies went out and played. We left Dustin alone and didn't say much to him. We figured the last thing he'd want was to play golf. He came out on the third or fourth hole and asked us why we didn't invite him.
Golf Channel analyst
I hadn't yet met Dustin in 2007, but we share the same agent, and we both played in the Desert Marlin, an off-season hit-and-giggle. At the event, I'm talking to some people, and this guy comes up and goes, "I'm Dustin Johnson. It's really nice to meet you." He called me "sir"—the first time anybody had called me "sir." He never didn't say "Yes, sir," "No, sir," or "Mr. Chamblee." He was that way with everybody. He was the right amount of confident and comfortable, but not arrogant. I couldn't have been more impressed.
CLAUDE HARMON III
We were on the plane after the  Tour Championship. [Johnson was co-leader entering the final round but shot 73 on Sunday; McIlroy won the Tour Championship and the FedEx Cup.] I said, "Hey, tough day." He said, "I didn't deserve to win the FedEx Cup." I said, "You had a chance, and if Ryan Moore makes a few putts, it would have gone your way." He said, "Listen, my bank account would have loved that, but that's not how I want to win the FedEx Cup. I don't want to win it by someone beating Rory McIlroy and doing my job for me. I should have done the job that I had to do.”