Fairley and Suh are great building blocks.
Get rid of Avril because he wants to much money, and KVB because he's a dinosaur now. Draft a replacement DE, either in the first, second or third rounds. You don't need someone spectacular when you have Suh and Fairley in the middle.
As for the secondary we have to resign Chris Houston. He's been having a great year so far despite everyone else on the secondary sucking. I'm conflicted with Delmas. I love his play and the attitude he brings to our defense overall, but at what price financially?
In the draft we either go LB with Manti Teo or Jarvis Jones or go for an explosive DE like Damontre Moore/ Bjoern Werner.
Get a decent DB through mid round draft or Free Agency.