I strongly believe with the fast pace offense with speed around the league we are seeing a paradigm shift in offensive philosophy. Part of the strategy is to wear out the defense.
The new defense required to combat the evolved (you can all it rehashed) offense has to be SPEED and DEPTH. You will need guys chasing from sideline to sideline but also need depth to rotate in players to keep them fresh. Because tired players miss tackles and that's how you give up big plays.
Speed is easier to obtain then depth in the current NFL system. To begin this new defense the first order must be increasing the speed and depth of the D line. On paper we may look OK with Ware, Ratliff, Lissamore, Hatcher and Spencer/Crawford. But Ratliff and Ware were injured. Crawford is an unknown and Spencer is unsigned. Even if they all stay healthy, you cannot expect Ware/Spencer to rush the passer and chase RG III/Chip Kelly offense all year.
I fully expect DL, another fast LB who can play multiple positions to be focus of the offseason. Oh, let's not forget OL/S.