Matt Millen left the TV booth to become the general manager of the Lions.
It did not turn out well for him.
John Lynch left his post as a TV analyst to become the 49ers' GM.
On Tuesday, Millen offered his advice to Lynch.
"Learn as much as you can, that's the first thing," Millen told Greg Papa on 95.7 The Game. "Make your own mistakes, that's the second thing. One of the things that I did not do well -- I would watch the film, I would do my homework and I'd have my opinion and then I'd say, 'OK, I like this guy better than this guy,' -- and then we would get into a meeting room and there were guys who did this for a living ... and I kind of let them have more say than myself.
"As I said -- you make your own mistakes. I should have kind of relied on my own instincts, and he (Lynch) should too."
The Lions went 31-81 in Millen’s seven seasons as general manager until he was fired after the 2007 season. The Lions went 0-16 in 2008.
Millen also shed light on the politics that go on behind the scenes -- the variables that have nothing to do with what goes on between the lines.
"Football is easy. You've been studying it your whole life," Millen explained. "It's not like it's an easy game, but you understand it. You understand what you're asking a player to do, you can see if the guy can do it, you can see if they fit, all that kind of stuff.
"The hardest part is managing people. In the end, it's always a people game. Always. You're managing people, you're trying to read people, you're trying to decipher the agendas, you're trying to decipher politics, you're trying to see which one who says he's on your side but isn't on your side ... there's all kinds of crap.
"And I'm not a political guy. You ask me a question, I'll give you the answer. There's people who don't do that. And that's the part -- you gotta learn the building. You gotta learn where all the booby traps are. You gotta learn who's on your side.
"And he'll (Lynch) do that. It just takes time. That's why it's tough for him to walk into a building that he's not familiar with ... John will be diligent; he'll be meticulous. He's a bright guy ... he's gonna need somebody that he can trust. Those are hard to find. Hopefully he gets that."