The Broncos D is not that deep in the front 7.  If Peko or Wolfe miss a game or two, opposing teams will run straight through the middle.  Even inside linebacker position lacks depth behind Marshall and Davis.  And Von Miller is indispensable.  
Broncos have some depth in the secondary....especially at the safety position.  Solid young players to back up Ward and Stewart.  
But the defensive line is a definite concern.  The starters right now are Wolfe, Peko and Crick.  Ideally, Crick should be a backup rotational player.  But Broncos have no one better.  Gotsis has shown nothing to warrant excitement.  Walker is a rookie.  Kerr is a big body but he has got pushed around a bit in preseason.  Broncos should look for some veteran help with the cutdowns.