As Mike Vandermause of the Green Bay Press Gazette points out, it is Ted Thompson - as opposed to the popular scapegoat Dom Capers - who has failed to arm this defense with sufficient talent. There's no true 3-4 defensive end on the team, leaving Ryan Pickett to play out of position next to B.J. Raji.
It actually seems as though Green Bay might be better suited to play a 4-3 defense - which is the only situation where I could see Dom Capers being fired - with Raji and Pickett inside and Nick Perry sliding back to his more natural defensive end position. Desmond Bishop becomes the true middle linebacker, Clay Matthews plays the Von Miller role as an outside linebacker and you have Brad Jones, who is already the best cover linebacker on the team, to move back outside.