CHICAGO - Kevin Jepsen won’t be driving a truck on Friday, won’t be selling real estate, won’t be approving time cards for his employees at some small business in suburban Phoenix. He won’t be doing homework for grad-school classes, nor will he be … well, is there anything else you’re glad you won’t be doing, Kevin?

“I don’t like to think about it,” Jepsen winces.

Understood. But there was a time when any of those occupations would have seemed more likely today than sitting in the Twins’ bullpen at U.S. Cellular Field, waiting for the chance to retire three White Sox hitters and celebrate another save. See, somewhere around Halloween 2007, Jepsen made a difficult decision: He retired from baseball.

“I was done. I told my wife, ‘I’m not playing anymore,’ ” Jepsen said. “The constant pain, it just wasn’t worth it, not with the results I was getting. I’ve got a 4[-plus] ERA and I can’t even get out of [Class] A ball? I mean, it’s not happening.”

So here’s the funny part about Jepsen’s career: Retiring was the best thing he ever did. Retiring saved his career. Retiring from minor league ball made him a major leaguer, an Olympic medal-winner and, lately, perhaps the most important pitcher on the Twins’ roster.

That’s because Jepsen, then 23 years old and three seasons removed from surgery to restitch the labrum in his pitching shoulder, an injury that had nagged him with constant soreness ever since, stopped doing shoulder exercises, quit his offseason throwing program, and shelved his regular workouts. He was considering what to do next, looking into applying to colleges, when his wife, Andrea, pointed out that, since they lived only a short drive from the Angels’ minor league facility in Mesa, Ariz., he might as well report to camp, tell the Angels his plans, and what the heck, give pitching one last shot.

Jepsen sensed that the Angels weren’t exactly disconsolate that he wanted to leave. They had drafted him as a starter, projecting him eventually toward the front of their rotation, but the shoulder surgery had forced him to the bullpen, with mediocre results. “To be honest, I think the only reason they were keeping me around anyway was that I had been a second-rounder [in 2002], I still had velocity, and I wasn’t costing them anything” beyond the $750,000 bonus he had received when he was drafted, Jepsen said.

So there was nothing at stake for anyone, really, when Jepsen took the mound and discovered something amazing. “There was no pain. I mean, it was gone,” Jepsen said, still amazed more than seven years later. Doctors theorized that his dedication to strength work, to building up the shoulder every offseason, never gave it time to heal completely. “I hadn’t worked out, hadn’t even picked up a ball, and I guess the pain went away. I kept waiting for it to come back and it never did. … It was pretty exciting.”

Suddenly, it was a joy to throw his 97-mph fastball and late-movement curve, a joy for everyone but the hitters. Jepsen was assigned to Class AA, tore through 31 innings with a 1.42 ERA, and was quickly moved to AAA. He was invited to the Futures Game in Yankee Stadium’s final year, but couldn’t go because of an untimely illness. But he was also selected for Team USA, sent to the Beijing Olympic Games (where he was a teammate of Brian Duensing), and was on the mound when the Americans clinched a bronze medal by beating Japan.

And when he returned to America, he had an even better assignment. On Sept. 8, he was summoned into a game at Angels Stadium in the eighth inning, handed the ball, and told to retire Derek Jeter. Three pitches later, Jepsen scooped up a bouncer to the mound, threw to first, and he was officially a major leaguer.

From there, he had six seasons of various success in the Angels’ pen, setting up closers like Brian Fuentes and Ernesto Frieri, getting outs “but really not understanding how,” he said. “I had good velo, so I was basically winging it.”

That changed after a late-2013 meeting with Angels scout Nick Francona, son of Indians manager Terry Francona and a baseball analytics expert, who proved to Jepsen the overriding value of first-pitch strikes. Stop nibbling, stop worrying about getting beat with your first pitch — you’re far more likely to be hurt by a 1-0 or 2-0 pitch.

Simple-sounding advice, perhaps, but “it was so convincing to hear, to see the facts, not someone’s opinion,” Jepsen said. “It taught me how to pitch. Get ahead, no matter what, so hitters have to chase.”

That knowledge, in turn, has made him more confident, and his present manager has noticed. Jepsen was promoted to interim closer when Glen Perkins was injured, and he’s 7-for-7 in save situations.

“He’s not overwhelmed by situations or ballparks or pennant races or any of that kind of stuff,” said Twins manager Paul Molitor, grateful for an effective fill-in for his All-Star closer. “He has a nice demeanor to handle those type of intangibles that come with closing games.  I’ve been impressed by the command of his pitches, which was a little bit of concern coming over here. His changeup has been way better than I thought, especially against lefthanded hitters. He’s got three above-average pitches.”

And, in his first real chance to close games, he’s having a blast. “It’s a lot more fun. A lot more fun,” said Jepsen, whom the Twins acquired July 31 in a trade with Tampa Bay. “If you’re a back end of the bullpen guy and you don’t ultimately strive to be in that role, I feel like you’re sort of selling yourself short a little bit. You should want to be a closer.”

Hey, it beats driving trucks or selling real estate.