Damion needs to embrace the now and get in shape. He is a RS Junior and needs to be ready to start. We lose a ton of starter's snap, but Ben has been playing since he RS freshman year and Deontre played as a true freshman. Green was hyped but got to Lincoln late and wasn't going to be in the mix his first year. As Corn said, all of the guys on the roster were recruited into a 3-4. At some point, familiarity with the scheme has to be a plus.
That's all fine, but everything you just mentioned is an unknown. That is why there is reason for concern. That concern could go away in a hurry if they all play how they should, but we lost a ton of production.