Back when he was about 13 years old, native New Yorker Rich Kleiman was so obsessed with then-Knicks point guard Mark Jackson that he once posed as agent Leigh Steinberg and placed a crank call to former GM Ernie Grunfeld and scouting director Dick McGuire.

Steinberg was then the rep for Greg Anthony, who was going to compete with Jackson for the starting point-guard job as the brash new rookie entering the 1991-92 season.

Kleiman, Kevin Durant’s manager/business partner, posed as Steinberg and claimed on the phone that Anthony might hold out of training camp.

Kleiman was caught red-handed.

“Got in trouble, they called my parents,’’ Kleiman told The Post this week.

Jackson got traded after that 1991-92 season and Kleiman remained a Jackson diehard, sneaking out of his house to watch late Clippers games (10:30 p.m. EST) on satellite TV at a local Manhattan bar. The bartenders let him in as long as he didn’t drink.

Kleiman, whose childhood bedroom was filled with Jackson posters, now is a good friend of the ABC/ESPN broadcaster. Like some of Jackson’s allies in the NBA, Kleiman is stunned he’s not coaching.

“I knew he wasn’t the greatest point guard to ever play but every kid, every teacher, every friend, they all knew I loved Mark Jackson,’’ Kleiman said. “I had two teams growing up. The Knicks at the Garden and the team Mark was on. It’s one of those things where a childhood hero becomes a good friend.”

Jackson was fired by the Warriors in 2014, partly for not having an assistant-coaching staff on the same page while also having a rough relationship with ownership.

Nowadays, Kleiman thinks Jackson would be a wonderful fit for the Knicks if new president Leon Rose moves on from interim coach Mike Miller.

Kleiman gave his thoughts on Jackson Wednesday, three days before the Nets parted ways with Kenny Atkinson, jolting open another vacancy.

“I talked to him about it all the time – that you should be coaching in the NBA,’’ Kleiman said.

“He’s one of those magnetic personalities. When you get people who are that special and people follow, it’s not always the most conventional way of doing things. That disruptiveness is sometimes what you need to become great. He’s a very spiritual guy. The idea is his time will come but if it’s not meant to be, it’s not meant to be.’’

The Post reported Tom Thibodeau and Jeff Van Gundy will be on Rose’s short list. You can add Atkinson as a potential candidate, too, as he’s a former Knicks assistant who works well with younger players.

“He clearly deserves to be coaching in the NBA,’’ Kleiman said of Jackson. “Whatever team gives him a shot, you learn from your experiences and hone your craft. Mark is one of those people who can make people follow. He’s got an incredible way to motivate. He brings charisma to the situation and he knows basketball. He played 17 years in the league at a time when point guards weren’t relied upon to score. He didn’t look to shoot but he made people around him better. People who played with him swear by him.’’

Asked if he can envision Jackson coming back home to coach the Knicks, Kleiman said: “There’a few things in life that like would check certain boxes for me. If he ever had a chance to coach the Knicks, obviously I’d be over the moon. But more importantly he’d be a tremendous coach. Somebody who brings a certain amount of credibility to any room he walks into. He can’t help but infuse positivity into a culture. I’ve seen it.’’

Kleiman, whose production company with Durant, Thirty Five Ventures, just released a Stephon Marbury documentary, thinks Rose will make the correct choice. Now, Nets GM Sean Marks has to figure this one out, too.

Kleiman has harbored childhood dreams of running the Knicks but was never contacted by Dolan, probably because he failed to deliver Durant.

“I’m a big Leon Rose fan as a person,’’ Kleiman said. “Someone who knows how to manage people as well. I know he’ll make the right decision. He knows me well. He knows what I’d say about Mark Jackson.’’