The Average Tenure Of An NFL Head Coach

Honestly, an offensive or defensive coach doesn't matter as long as they allow the OC the autonomy needed to build a successful offense and you won't have a successful offense unless you build one that is built around your QB. The days of development is dead. Screw Tom Brady but he was absolutely right talking about today's football. But moving off that rant...lol.
Yea, this opens the question, what really happened with our defense? (Sean was 100% involved in his offense and the results showed and stayed consistent) Did our defense regress because DA tried to spread himself too thin? With that said, its no excuse, because a great coach wins with back ups. (The Cinci coach winning last week with their back up Qb was pretty special imo)