The Bills hired Rob Ryan. Rob and Rex will run the defense while “defensive coordinator” Dennis Thurman will handle defensive backs.
Considering that Rob Ryan is probably the worst defensive coordinator in the NFL and that Rex Ryan took a 4th-ranked defense and turned it into near the bottom of the barrel, this is a terrible sign for Buffalo.
The truest thing anybody ever said about Rob Ryan comes from Mike Tanier:
Coverage: The Saints have trouble getting the play in from the sidelines. Defenders are looking at Dennis Allen on the sideline shrugging their shoulders. Kenny Vaccaro is actually calling Rob Ryan on his cellphone. Also, there are only nine Saints on the field.
Other teams think: Quick-snap the ball and just fling it to Johnson, the way the Jets did when the Titans got mixed up and left Brandon Marshall uncovered!
The Lions think: We need to be unpredictable. This might be a good time to get T.J. Jones involved.
Yeah, we’re having a lot of laughs at Jim Bob Cooter’s (and Dennis Allen’s) expense. But it would be worse if Joe Lombardi were still coordinating the Lions plays and Ryan were trying to stop him.
Fan in the stands: “Johnson is going to clear out deep, with Tate running an in-route.”
Guy on Twitter: “Johnson is going to clear out deep, with Tate running an in-route.”
Richard Sherman, watching from home: “Johnson is going to clear out deep, with Tate running an in-route.”
Lombardi: “Let’s have Johnson clear out deep while Tate runs an in-route.”
Ryan: “I smell a running play.”
36 Chambers - The Legendary Journeys: Execution to the max! 
P.S., I believe this is karmic retribution for joking about how the Browns should re-hire Mike Pettine as their defensive coordinator.