Peterson had passed on his initial college commitment, instead signing with the Twins after being a 49th-round pick in the 2002 First-Year Player Draft. From there, he climbed methodically through Minnesota's system before eventually stalling in Triple-A. The Twins released Peterson after the '10 season, and it was only with the urging of some baseball buddies that Peterson agreed to try the Independent League.
A two-year stint with the Bridgeport (Conn.) Bluefish followed, during which Peterson rediscovered his love for the game. But he also faced an approaching reality. That contract he signed with the Twins back in 2002 included an agreement that the organization would cover his college costs, should he go back to school within two years of ending his career in affiliated ball.
With time running out before that offer would be null, Peterson, on Aug. 14, 2012, decided it was time. He would register for online courses with the University of Phoenix and see where his career took him from there.
Only, the Cardinals intervened.
Just hours before he was to sit down at the computer and officially choose his classes, a phone call put a pause on Peterson's plans. The Cardinals -- their analytics department having identified Peterson as someone who still had some promise -- signed him to a Minor League contract that day. His career resurrected, Peterson has thrived since.
And on Saturday, his circuitous journey through the ranks of professional baseball culminated with his first Major League callup.
"I've waited a long time for this, and for it to finally happen, it just really means a lot to me," said Peterson, who took the roster spot vacated when Matt Holliday was moved to the disabled list. "I think it means a lot more to me now than it would have at 24, 25 years old."
As storybook as this moment in Peterson's tale may be, his summons to the Majors was not made simply as a reward for resolve. He has been Triple-A Memphis' best hitter this season, collecting a league-most 22 homers, 66 RBIs and batting .306 in 93 games. Three days ago, he was playing in the Triple-A All-Star Game.
"For us to be able to give him this opportunity, I think it's really special," general manager John Mozeliak said. "Very few times do players play 11 years in the Minor Leagues, because usually they either quit or they are told to quit. For him to persevere, it's really a special story. As you can imagine, we're pulling for him and we hope he has a lot of success."
Peterson learned in between games of a doubleheader on Friday that he would be spending his Saturday morning driving to St. Louis. Believing that he had been passed over for a big league promotion several times with Minnesota, Peterson had learned long ago not to expect anything.
That's why he had paid little attention to the Cardinals' roster situation and gave almost no notice to his own Minor League numbers.
"I've learned over the years that that just fills my mind with stuff," Peterson said. "[The 2010 season] wasn't a lot of fun for me. I thought I was going to get my chance and I didn't. Just being younger, you look at things differently.
"In 2011, I had pretty much given up. But I had some good buddies and a good support system that finally after a couple months talked me into going out there and giving it a go."
That was when Peterson tried Independent ball. Bluefish manager Willie Upshaw tutored Peterson through some minor tweaks last season, including changing the position of the first baseman's hands on his bat. Peterson said he saw -- and felt -- immediate results.
Peterson was batting .293 with 21 homers, 21 doubles and 68 RBIs at the time the Cardinals called.
"I just learned what kind of hitter I need to be," Peterson said. "I was honestly trying to be the hitter someone else wanted me to be instead of just being myself for a long time. I just changed my grip a little bit really, and it really loosened the swing up and let the ball travel."
Peterson slides into a bench role with the Cardinals, and the club is comfortable playing him at first and the corner outfield spots, if needed. And though Holliday is expected to come off the DL in a week, Peterson has the opportunity to make his stay longer.
With Ty Wigginton no longer in the picture, Peterson could fit as the power-hitting, right-handed bat off the bench that the Cardinals have lacked this season. The organization will have to weigh that against retaining three catchers.
With Memphis this season, Peterson was hitting .341 against lefties and .301 with runners in scoring position.
"His eyes are spinning a little bit right now, and rightfully so," manager Mike Matheny said. "He's very excited. It's a great story. Nothing has been given to him. He's had a tremendous season down there and I think he will fit in very well to what we're doing around here."