It wasn’t a promising beginning.

The first time Michael Greller caddied for a teenage named golfer Jordan Spieth, he gave him bad information. “The first hole I caddied for Jordan, I gave him a bad number. I was so nervous. We started on No. 10, but I gave him a yardage for No. 1,” he told GolfChannel.com in 2013. “He wasn’t flying under the radar; he was expected to win. Anything less than a W, and we didn’t meet expectations.”

That was the 2011 U.S. Junior Amateur at Gold Mountain, not far from Greller’s home near Seattle. Greller, a sixth-grade math teacher, had been moonlighting as a caddie for local tournaments. It’s something he enjoyed, though he hadn’t really considered it as a career.

Spieth won the tournament and, the next year, he wanted Greller by his side for the 2012 U.S. Open. That’s when Spieth became the top-ranked amateur worldwide — and Greller became his full-time caddie.

Greller, now 37, is on a much different career path today. He’s the caddy for a 21-year-old Masters champion. The average salary for a teacher in Seattle with 15 years experience is $77,000. He likely earned closer to $375,000 during the past month, according to an estimate by Business Insider’s Tony Manfred. Still, in some ways, Greller said it feels like he never really left the classroom.

“Everything I have done in my life prepared me for this, specifically teaching for 10 years,” he told the Seattle Times last year. “Being able to think on your feet, being adaptable and having thick skin … you are going to mess up — and if you are not confident in yourself, your player picks up on that. You have to be willing to serve and encourage. Just like in teaching.”

“Now it’s the same thing,” he told Golf Digest, “except I have one kid.”

The partnership was a long time coming. In 2006, Greller went to watch the U.S. Amateur Public Links Championship near his home in Gig Harbor, Wash., and saw a player dragging his own bag around the course. He walked up to him and said he would to carry it for him. “We offered to pay him and he refused,” the golfer, Matt Savage, now an assistant golf coach at Florida State University, told the Wall Street Journal.

It wasn’t about the money. Greller enjoyed it — so much so that he moved in order to be near Chambers Bay, a public golf course near the school where he could work part-time as a caddie. But he also loved teaching. After working amateur tournaments, he would take his yardage book back to the classroom and have his students do the math, according to Golf Digest. “It’s kind of eerie how much it translates,” he told the magazine.

Years after Greller volunteered to help Savage, Savage introduced him to a friend, another amateur named Justin Thomas, who needed a caddie for a local competition. A year later when Spieth needed one for the 2011 U.S. Junior Amateur, Thomas recommended Greller for the job. The two soon forged a connection — Greller, a teacher leaving his classroom, and Spieth, a student leaving school to pursue his dream.

“I took a one-year leave of absence from teaching, thinking [Spieth] had no status anywhere,” Greller told Golf Digest. “Yes, he was the No. 1 amateur in the world, but that means nothing out here. I was getting married, had a house. To go chase this kid caddying was kind of a big risk. And then he went crazy.”

Several months later, Spieth, dropped out of the University of Texas and hired Greller, according to GolfChannel.com. But over the past few years, Greller has become something more — maybe a mentor, maybe a friend.

“Every day, someone asks if we were teammates or classmates. I always tell him it’s because of his receding hairline. I get a kick out of that,” Greller told GolfChannel.com, with a laugh. “I see it more as a brotherly relationship. We compete hard and talk a lot of trash. I was born and raised in Michigan. He picks on my teams; I rag on his Texas teams.”

“We give each other a lot of crap,” Spieth added. “It’s almost like a brother situation. We fight over the dumbest things, like sports.”

But perhaps most importantly, Greller knows how to handle Spieth on the golf course. For instance, when Spieth double-bogeyed at the 17th hole on Round 3 of the Masters tournament over the weekend, Greller kept him calm on the way to the 18th, according to the Wall Street Journal.

“You don’t want to over-analyze or make it harder than it is,” Greller told the newspaper. “I just try to be a calming influence on him. He’s very intense.”

“Being an encourager, I think that’s huge for the young kid out here because you’re going to have ups and downs, and you’re figuring out how to deal with that,” Greller told the New York Times. “So I’m always trying to encourage him. If he needs to let things go, I’m the person he’s going to bounce it off of. And just being able to adapt to situations, that’s something you have to do out here that I’m comfortable with from teaching school for so long.”

Those in the field know how rare it is for a new champion to hire an amateur caddie.

“You have to be really lucky to get into that position,” PGA Tour caddying veteran Mike Kerr told the Wall Street Journal. “But the way they work together, it looks like he’s been doing it a long time.”

Greller acknowledged that there are many qualified for the job but none with the relationship he has with Spieth.

“He’s very positive, he’s very patient and he doesn’t really react too much,” Spieth told the New York Times. “He’s one of the most competitive people that I know, but he doesn’t show it on the course, which is very helpful. He’s not living or dying on putts.”

“He brings a nice voice to me when I need it,” he added, “especially in the heat of the moment.”