The ILB, S, and CB is where the defensive injuries took a huge toll and its where Blubaugh(F), Shannon(F), Rastas(RF) were called into service long before i think anyone thought they would be ready to contribute at a high level. I also think that all three of them would have looked substantially better if they were the only one of the 3 on the field at one time.
So much of football is about confidence and momentum. IMO Blubaugh will be a player when the guys around him are all solid, the defense is stopping the run and also able to get pressure on the QB. Shannon looked the best of all three of them IMO, but the nature of his position is much different than CB or ILB. I don't think Rastas will ever be able to be the guy at ILB, I think if he can put on 20-30 lbs of good weight he can be a solid spot duty guy as long as the other ILB is very solid. In UND 3-4 scheme the ILB and S play huge roles in bringing pressure and the CB in being able to cover for 3-5 seconds.