They have 6 positions in the starting lineup they need to fill by either resigning last years starter or replacing with a FA : LT, C, Edge, WLB, S and CB. They can't fill all of those positions on the cheap or the the draft so i agree they will have to create a bunch of cap space. They can do some financial shenanigins, but they seem to like to keep that to a minimum.
Plus they need to add depth at numerous positions, although some or most of that can be done with lower cost guys.