But when you have coached football for nearly 40 years as has the 60-year-old Marinelli, you know you win some, you lose some. And if you get the chance to continue in NFL coaching depths and peaks with an unmistakable, oozing passion, you leap.
"It's been, what, seven months now," he said, as if needing a reminder of the conclusion to the worst season in NFL history. "Tremendous opportunity for me. Tremendous people in Detroit. I always put it on myself. I did not do the job.
"This is a special place for me, a quality organization, and it's special because of Lovie (Smith). It's one of the real driving forces behind this. We had the chance to work together so much before. We were part of the beginning of change in Tampa Bay in 1996. We share a strong belief in the system. It's in place. There are good players. I hope I can inspire, provide a base of knowledge and improve each man's game."
Why Marinelli could not build it in Detroit and turn the Lions into winners has provided muddled debate among his peers. Was it poor organization and support behind him or simply a man who was overmatched, a stellar position coach who should have remained just that?
He has more prime defensive players in Chicago to further instill Cover 2 core principles -- a pass rush that relies on the front four, that pass rush and coverage working in concert, a focus on hustle and speed to the ball, re-routing receivers and trusty tackling.
Blitz when you want to, not because you have to.
Do not defend as much as you create chaos for offenses.
Max out on every snap.
The Bears open training camp on July 31. In offseason drills, Marinelli has seen his defensive line group show plenty, enough that it can become dominant. Everything starts with tackle Tommie Harris. Ends Adewale Ogunleye, Alex Brown, Mark Anderson and young players including rookie Jarron Gilbert have impressed Marinelli. He sees depth. He sees a group that was a huge part of the Bears drive to Super Bowl XLI two years ago.
"Tommie is strong, motivated, bright, perfect for the system," Marinelli said. "He was banged up last year. He seems pretty healthy. He's done it. This group is going to compete. It is exciting to see them come together."
Herman Edwards was part of that original Dungy staff in Tampa Bay. Edwards expects a Bears defensive renewal this season. He likes that Smith will call Bears defensive signals in 2009. He emphasizes that the Smith-Marinelli relationship -- both as friends and coaches -- will impact not only the team but the franchise in lasting ways.
"I think this is one of those coaching moves of this entire season that is going to bring big dividends," Edwards said. "Rod is one of the best, if not the best, defensive line coaches in the league. I look for Rod to help that entire defense overachieve."
Just getting back to winning football games would be plenty for Marinelli.
"This is so exciting for me," Marinelli said. "This is something I adore. When I think about the chance to coach football for such a long time, I don't think Xs and Os. It's the friends, the relationships, respecting this game and trying to make it better. It's another opportunity to do that and coach, and that makes it another great day."