Michael Greller thought he had the perfect summer job.

The sixth-grade math teacher signed up as a caddie in 2007 at Chambers Bay, a new golf course on the edge of Puget Sound, where he made between $60 and $100 a bag.

The previous summer, Greller got hooked on this hobby when he was watching the U.S. Amateur Public Links at Gold Mountain, his home course near Seattle, and he noticed a college kid who didn't have a caddie. Greller offered to work for free.

The payoff from the relationship he started that day and those that followed was more than he could have imagined.

One year into this summer job, Chambers Bay landed the 2015 U.S. Open and Greller began dreaming of walking the fairways with the world's best players. He had kept in touch with that college kid, Matt Savage, now the assistant golf coach at Florida State. He thought Savage might know of some young players who could use a caddie, or perhaps he could find a qualifier who needed local knowledge on a course unlike any other used for a U.S. Open.

Greller only wanted a chance to caddie in a U.S. Open. He knew it would be a long shot.

"And now it's my fourth U.S. Open," Greller said, shaking his head at this improbable turn of events. "And I'm caddying for the Masters champion."

His boss is Jordan Spieth, the No. 2 player in the world who joins Rory McIlroy as the top favorites when the U.S. Open starts on a course that Greller has walked more than any other.

"It will be a cool experience for us," Spieth said. "And he's definitely going to come to the plate with more than the other guys can bring."

Greller downplays the course knowledge for a couple of reasons. Chambers Bay has changed significantly from when it opened in 2007, and especially after the USGA saw how the course performed at the U.S. Amateur in 2010. He hasn't caddied there since 2011. Last month, he walked the course with a local caddie to get reacquainted.

"People think I'm some guru around there. I'm really not," Greller said. "The biggest advantage is having my own bed and a familiar environment. I know it better than the average guy. But I work with the best caddies in the world. They're going to figure it out."

Everywhere he turns will be a reminder of how far Greller has come.

A couple of his former students at Narrows View Intermediate have signed up as standard bearers. The principal at his old school is the head marshal on the 10th hole. One of his poker buddies is now a police officer and has been assigned to be part of Spieth's security detail.

"So many people in my life that I know are directly involved in the U.S. Open," Greller said. "It's going to be fun to look around at all those faces."

It's a shame Savage won't be there. He was the key figure in this odyssey.

Greller grew up in Michigan, played small college golf for Northwestern Iowa and moved to the Pacific Northwest to be near his sister. He earned his Masters' degree and found work outside Tacoma through a job fair.

School had just let out in 2006 when the U.S. Amateur Public Links came to town. Greller wanted to watch the best amateurs on his golf course, so he decided to walk with Clay Ogden, the defending champion. Ogden happened to be playing Savage, who had just completed his freshman year at Florida State.

"I think I was the only player walking around Gold Mountain carrying my own bag," Savage said. "Michael followed my group. He and my dad talked the entire time and he sat down and had lunch with us and offered to caddie. He said, 'I don't want to get paid anything, I just want to be part of the event. It's my home course.' After spending an hour or so with him, I could tell he was an awesome guy, really down to earth. I didn't think he'd get on my nerves like some random guy."

Savage advanced to the quarterfinals before he was eliminated, and they kept in touch. Greller had so much fun that he transferred to a school near Chambers Bay so he could caddie during the summer when the course opened.

Four years later, Savage called Greller.

There was a 17-year-old at Savage's home club outside Louisville, Kentucky, named Justin Thomas — his father, Mike Thomas, was Savage's club pro at Harmony Landing — and the kid needed a caddie for the U.S. Amateur at Chambers Bay. Greller and Thomas hit it off and reached the second round.

What followed was an eventual fork in this amazing road.

Thomas and Spieth have been close friends since they were 14, so when Spieth went out to Seattle in 2011 for the U.S. Junior Amateur, Thomas pointed him in the direction of Greller. Spieth wound up winning his second U.S. Junior, and the next year, Spieth asked Greller to caddie for him at the U.S. Open. Spieth was low amateur at Olympic Club.

Spieth turned pro and asked Greller to come with him. Greller decided to take a one-year leave from teaching, knowing he could always return if it didn't work out.

It worked out.

Spieth had no status on any tour. By the end of the year, he won a PGA Tour event, was the youngest American (19) to play in the Presidents Cup and finished No. 10 on the money list at nearly $4 million. Two years later, Spieth became a Masters champion with Greller at his side.

All because of one selfless offer. All because of one chance meeting.