Winter Garden, Fla. — Greg Mattison pulled up a chair and made it clear he wasn’t leaving.

That was more than 30 years ago, outside a different Coach Harbaugh’s office. But as impressions go, that first one isn’t all that different than the one Mattison is leaving now, as a football lifer whose 40-year coaching career has come full-circle in more ways than one.

Mattison returned to Ann Arbor nearly five years ago, at the urging of his family and the request of his longtime friend, Brady Hoke, to serve as Michigan’s defensive coordinator.

But that he stuck around after Hoke was fired last winter, embracing a lesser role as a well-compensated position coach — the lone holdover retained by Jim Harbaugh, who was hired amid much fanfare a year ago Tuesday — came as little surprise to those who know him best.

Jack Harbaugh, for one. The football patriarch laughed Tuesday as talked about the day he accepted his first college head coaching job. This was back in 1982 at Western Michigan, and only hours after he’d returned to his new office to start putting together a staff, there was a knock on the door.

“I opened it and there was a guy that I’d never seen or met before,” Harbaugh said, telling a story he’s told many times over the years. “Never talked to him in my life. Didn’t know him from a sack of sour apples.”

Didn’t know Mattison, who’d spent the last year working at a sporting goods store in La Crosse, Wis., had talked to his new athletic director about landing an interview for a job on Harbaugh’s staff, either. But that didn’t matter to Mattison, who wore a sport coat that was “just a little too tight” and told Harbaugh flatly, “I’m not leaving until you hire me.”

He meant it, too, refusing to take no for an answer, pulling up a folding chair just outside Harbaugh’s office and waiting for hours on end.

“Every time I went out he’d sort of wave to me,” chuckled Harbaugh, who finally let him tag along later that day when he went to grab dinner, then relented and penciled him in for a 2-hour interview the following afternoon.

Once Harbaugh let Mattison in his office and put him on the blackboard diagramming what he knew, “He was dynamite.” By the time he left, he was Harbaugh’s new defensive line coach.

Bridging the gap

The interview process was a little different this time around. Mattison certainly was no stranger to Jim Harbaugh, and not just because of his lengthy track record as a defensive coach and a well-earned reputation as a one of the nation’s top recruiters at elite programs like Michigan, Notre Dame and Florida.

He’d returned to Michigan in 2011 for his second stint as the Wolverines’ defensive coordinator after three years in the same role on John Harbaugh’s staff with the Baltimore Ravens. And though the dismissal of Hoke as head coach hit him hard — “Greg doesn’t have a better friend than Brady, and Brady doesn’t have a better friend than Greg,” Jack Harbaugh said — he’d vowed to make Michigan his last coaching stop.

So when Jim Harbaugh hired D.J. Durkin as his defensive coordinator, Mattison — one of Durkin’s former mentors — agreed to stay on as the line coach.

“And for him to commit to the players, really — to the players and the program — it was huge,” Jack Harbaugh said. “It gave credibility to Jim, with Greg being here.

“When you have a coaching change — and I was a part of a lot of them — and that new guy walks up there and these seniors look at you and wonder, ‘What’s this mean for me?’ … Well, for somebody to be here to bridge that, that’s so important.”

Important for Harbaugh and Durkin, sure. But also for Mattison, who’ll get another chance Friday to call the shots as coordinator in the Citrus Bowl against Florida, with Durkin accepting the head coaching job at Maryland earlier this month and his newly hired replacement, Don Brown, busy getting settled in Ann Arbor.

‘Nothing could be better’

After that, he’ll get back to doing what he does best. Back to recruiting, with Rashaun Gary, the nation’s No. 1-rated recruit, among the Wolverines’ primary targets. And back to coaching the defensive line, a job Mattison reveled in this season — all the injuries notwithstanding.

The Wolverines lost key contributors up front, from Bryan Mone before the season to Mario Ojemudia and Ryan Glasgow during Big Ten play, but still racked up 30 sacks and 89 tackles for loss — third-most in the Big Ten — en route to a top-five national ranking in total defense.

Yet for the 66-year-old Mattison, scheduled to make $500,000 in the final year of his contract in 2016, this is where he starts getting a little choked up, talking about seeing the players he recruited — guys like Chris Wormley, Willie Henry and Desmond Morgan — come into their own as seniors.

“I kind of raised them as babies,” he said Tuesday after practice at West Orange High, and that’s something he hasn’t had a chance to do that in more than a decade, since his days at Notre Dame.

“The amount of things that we’ve been through since I’ve been here — the ups and downs — it’s been a journey,” said Morgan, a fifth-year linebacker who’ll play his last game Friday. “But he’s a great guy to go through it with. He’s a tremendous coach, and a great mentor for me as well, in a lot of ways.”

And in a lot of ways, this all makes sense, too, with Mattison — in his uniquely affable way — bridging the generations.

“That’s the great part of being somewhere for a long time, because you get to take a young man and wonder how good can he be?” Mattison said. “And then all of a sudden you’re talking to his parents about what agent he should get and you see him walk out with a degree from Michigan. Are you kidding me? Nothing could be better. That’s why I coach.”