I just can't see Ryan as a fit in Buffalo - he's everything Buffalo isn't (kudos to Buffalo). Great fan base up there...nowhere near the level of trash-talking stupidity I see with the Jets.
And yes, they have a very good defense.
Mario Williams turning 30 with cap hits next three years: 19.4, 19.9, 16.5...
Three linebackers (including Spikes), two DEs (including Jerry Hughes, 10 sacks each of last two years, and Jarius Wynn) and a starting safety (Searcy) are UFA...as is CJ Spiller.
They have no first round pick. They have no QB.
They are a solid team with some structural issues. I'm not going to underestimate them, but neither am I going to start the hand-wringing. Their DL has been playing top-notch for a couple of years now - whatever the coaches have been doing (grab and loop, anyone?), it's been working. I don't see Rexy Ryan suddenly creating some huge upswing in that unit, because it hasn't been the problem.
The problem is in the very same area that Rexy created with the Jets. I think Fox would be a much better fit in Buffalo and would do more with the current roster, honestly.
Ryan would likely have helped a team like the Patriots as a DC more than he will fix what ails Buffalo.