But nearly two years later, while working the night shift at the Kraft Foods plant in his hometown of Springfield, Mo., in the single-sliced cheese line, he had an epiphany.
"It was the spring of 2008 and I was pulling into the Kraft employee parking lot when it sank in that I had to get back into the game," recalled Hart, who will make his official coaching debut next month with the Texas Rangers' complex-level Arizona League team.
"I realized the Lord blessed me with an opportunity to be in baseball and I needed to ride that train as long as I can."
Hart called the Rangers to talk about the possibility of moving into the dugout with them at some point in the future.
Knowing that there was little chance of a job opening in April, he figured that perhaps he might get on their short list for the '09 campaign. But luck or fate or karma was on his side.
"It so happened they needed someone to fill in as an assistant coach in Clinton [Iowa] in the Midwest League, so it was perfect timing," he said. "They said, OK, we'll see you in Clinton on Opening Day. I didn't go to Spring Training at all."
And so Hart headed back to the Midwest League, technically as a player-coach, where he spent the '08 season.
For Hart, climbing through the ranks a second time will be child's play compared to what he's been through.
Originally a fifth-round pick in the 1998 First-Year Player Draft out of Southwest Missouri State by the Oakland Athletics, the first baseman's numbers were off the charts in his first few seasons. He made Northwest League All-Star status in his debut at Southern Oregon with 20 homers, and he batted .305 with 19 home runs, 48 doubles and 123 RBIs in his first full season at advanced Class A Modesto in 1999 after skipping past low Class A.
In 2000, Hart tore up the Texas League with Double-A Midland, hitting .326 with 30 home runs and 121 RBIs before moving up to Triple-A Sacramento in 2001. There, his numbers dipped a bit, but he still hit .247 with 19 home runs and 75 RBIs.
Hart was traded to Texas the following winter with catcher Gerald Laird and outfielder Ryan Ludwick for first baseman Carlos Pena and, after hitting .263 with 25 homers and 83 RBIs at Triple-A Oklahoma, made his Major League debut that summer with the Rangers, hitting .267 in 10 games.
He batted .252 with 21 home runs and 82 RBIs in the summer of '04 at Oklahoma but spent most of the season feeling like his timing at the plate was off. Hart then started visiting local doctors to try to figure out what was wrong.
Diagnoses ranged from a sinus infection to fatigue, and he went through courses of antibiotics, still suffering through raging headaches and balance issues, before an MRI finally revealed a brain tumor.
Hart spent the summer at home with Jenny as they awaited the arrival of their first child, daughter Kloe, and he recovered from the removal of the benign tumor. He savored the time with his wife, painting Kloe's nursery and laying down hardwood floors, before beginning a slow but steady comeback to the field.
It wasn't easy at first.
"As soon as I got on the field, I couldn't even stand up," recalled Hart. "I'd fall down shagging fly balls."
But come back he did, returning to the Texas League in 2005 with Frisco and being introduced to a standing ovation during that league's All-Star Game. He hit .246 with 21 homers and 77 RBIs that summer, and the next season, his last, he set the Oklahoma team record for career home runs when he hit his 58th in a Redhawks uniform in August.
But he knew that he was done playing.
"Being so blessed to come back and get to play two more years, it kind of changed my perspective," he said. "It's not that I lost the fire, but I knew I'd given it my best run and it was time to start a new chapter."
When the Rangers signed Hart to a player's contract, there was no intention of his actually taking the field. This was a chance for him to see if coaching would be right for him. And he knew right away it would be.
"I was kind of like a big brother to a lot of those players in their first full seasons," he said. "But I never got into a game and I didn't want to. As the year went on, I realized how much I really liked [coaching], how rewarding it was helping these guys get to the next level."
When the Rangers offered Hart an official coaching job for 2009, he was thrilled. He headed to Arizona for a few weeks to help coach the organization's instructional league squad and began making the transition from "friend" to "coach" for real.
"In Clinton, I wanted to build guys' trust and let them come to me with questions, rather than coming in and trying to coach them," he explained. "So when I got to instructs, I felt a little more nervous about being responsible, and I had my group of guys who looked at me as a coach more than a big brother."
Hart is still learning his own coaching style.
"Right now, I'm definitely still a 'gimme the bat and let me show you what I'm talking about' kind of coach because playing is still so fresh in my memory," he said. "I'm better at showing than explaining."
And the best part about his new job? The Arizona League plays all of its games in the Phoenix area, and most of the games are during the day. This means that every day Jason Hart will be able to coach baseball, and every night he'll be able to come home to Jenny, Kloe and Camden.
Lisa Winston is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.