June 17, 2010 was an unprecedented day for the Devils franchise when they hired their new coach. In Johnny Mac, he was the first former Devils player to become coach of the team.
It came with plenty of dues paid. He had been an assistant with the Devils starting in 2002, the year he retired from playing. He would serve in that capacity until 2009. Even then, in 2007, he was thought of to replace Claude Julien (Don't give me technicalities.) when Lou Lamoriello went with Brent Sutter instead. He was also thought of as a candidate when the 2009 search ended with Jacques Lemaire.
When Lemaire was hired, MacLean was reassigned to Lowell to be their head coach, a move that Lou felt was necessary. And it proved beneficial. The players that played under him gave him positive reviews, commonly saying that he coached like they were being prepared for NHL play. That season, Lowell also made the Calder Cup playoffs for the first time since the Devils moved their affiliation there in 2006, and the first time any AHL affiliate made the playoffs since 2000 when the Albany River Rats did so.
I think the original plan was to get 2 years of experience under his belt. That was the length of time Lemaire's contract was. However, Lemaire retired just days after the 09-10 season ended for them. Again, Johnny Mac's name came up for the job. (As did a lot of other names, mostly rehashes.) This time, however, he got the call.
When asked about what kind of hockey to expect the Devils to play under him, Mac simply said winning hockey. You wouldn't expect anything less. The only problem was winning hockey was not what he was getting. All kinds of problems had surfaced, some he had no control over, while others showed his inexperience in the position, and it lead to the Devils having the worst record in the League around Christmas time. Needless to say, he was gone by then.
Carolina gave him another chance when Kirk Muller, days after he was hired as their head coach in December, 2011, recommended his friend to be hired as one of his assistants. He would stay there until after the 13-14 season.
Since then, he has been working as an analyst on the NHL Network. Occasionally, he'll also join the MSG team in the studio.