Point is the team was in a different place when Rex was here, with different needs. The O-line had been put together, we needed skill position guys and brought them in. He needed guys who knew his defense from Baltimore and brought them in. By the second year when they brought in veterans like Holmes, LT and Taylor they were going for it, which means you're bound to slide back when those guys leave.
And again, Tannenbaum was the GM the whole time. This whole discussion is just MB's way of dodging the fact that Rex won here and took us to two AFC Championship Games. To do that you need to be a good coach, it's not been done by anyone else in our history, including Parcells, Ewbank, anyone.
Rex did well for his first two seasons. Rex never did well as a head coach again.
He and Sanchez were essentially suffering from the same issue: they came in and surprised the league, got figured out quickly, and never were able to grow beyond their initial success.
As far as the roster goes, Mangini built a lot of the infrastructure that allowed the team to succeed. Rex couldn’t build the team out long term in the draft. Even his free agent signings were less and less productive as time went on.
He got the skill players early and then he and Tannenbaum failed to build anything around Sanchez after 2011 and both of their work on ignoring the offense came back to bite them.
What really keeps this argument going is that you seem to either completely fail to realize that the team failed under Rex far more than it succeeded, or flat out ignore it.