Jeff Lageman was on the other end of the telephone line the other night reminiscing about the best times of his 10-year NFL career and about the man who helped facilitate those good times.

The Jets first-round draft pick in 1989 who signed as a free agent with the Jaguars in 1995, their expansion season, spent his final four seasons as a defensive end in Jacksonville, where he finally found joy in his NFL career after six losing seasons in New York.

Lageman always was an old-school, non-nonsense, stubborn football player — traits not at all dissimilar to the coach who signed him to play in Jacksonville: Tom Coughlin.

That’s why Lageman, who was an unofficial head of Coughlin’s veteran “leadership council’’ before he’d even come up with the idea years later with the Giants, watched from afar as his former coach said goodbye to the Giants on Tuesday and he insisted it was not a sad moment.

“I don’t think sadness is the right word, because he accomplished unbelievable things,’’ Lageman, now a Jaguars broadcaster, told The Post. “It definitely tugs at the emotional heartstrings a little, but … it wasn’t sadness, because I know he’s not done. If he wants to coach again he’s going to coach again.

“I know one thing: Tom Coughlin’s not going to retire and sit in a rocking chair and play with his grandkids every day. That’s just not the way he’s wired. He’s going to work until he can’t work anymore. His passion and his work is football and helping build winners and win championships. In some way, shape or form he’s going to be back in the game.’’

Lageman related to the endless stream of Coughlin’s players who have taken to social media in recent days praising their former coach with heartfelt thanks for what he did for their respective careers.

Coughlin made the game fun again for Lageman. Imagine that: The rigid coach with the persnickety military rules making the game fun again for a veteran player already set in his ways?

The perception of Coughlin, of course, always was the opposite — particularly in the early years of his career before he loosened his belt a little bit in an effort to adapt to the younger culture of players mid-way through his Giants career.

“It’s amazing that every player that ever played for him — if they didn’t have great respect for him while they played for him — almost to a man, once they finally grew up and realized what he was all about and was able to do for them, they would tell you they have great respect for him now because he made them better,’’ Lageman said.

Lageman experienced his moment of clarity with Coughlin earlier than many of his Jaguars teammates, because he recognized right away that Coughlin could give him something he’d been missing in first six NFL seasons — a chance to win.

“From probably the first meeting me and him had we kind of clicked,’’ Lageman recalled. “On my free-agent visit I sat down with him and he said, ‘What are you looking for?’ I said, ‘I’m looking to get the excitement back in football.’ I had lost in New York and that had taken the fun out of the game.

“I looked him in the eye and said, ‘Most importantly, Tom, I spent six years in New York and never had a winning season and I want to win.’ His eyes lit up. And from that moment on, me and him were fine.’’

Lageman called the Jaguars’ 1996 playoff run from a 9-7 wild-card entrant in the franchise’s second year of existence to the AFC Championship game in New England “the most fun I ever had in professional football.’’

Fasting forward 20 years later to his powerful Tuesday Giants farewell, the end game was not ideal for Coughlin. But how often is it for the great coaches and players?

“Twelve years as head coach,’’ Lageman marveled. “If you went to any owner in the NFL and said, ‘I’m going to guarantee if you hire this guy, in 12 years you’re going to have two Super Bowl titles,’ how many owners would turn that down? None of them. Absolutely none of them.

“So there’s no sadness no regret. For me, [Tuesday was] more of a celebration of what a great job he was able to do for the Giants in the biggest market there is in the NFL.’’