For MSU, having Layne sit really hurts.
Josiah Scott played in 4 games this year, missing the first 8 with injury. He sits the game, he comes back next year as a redshirt sophomore, he plays, he's going to be a junior. Sounds like he's playing. Tyson Smith retired in August due to ongoing medical issues. Josh Butler hasn't been cleared to play yet.
So of the two deep we went into camp with, the only one who could play has to burn a redshirt to do so. Sounds like we have a bunch of little used 2nd year guys back there with Shakur Brown, Tre Person and Dominique Long. We could also play true freshman Kalon Gervin without burning his redshirt. Not exactly the secondary you want to throw out there against the guy projected to be the first QB taken in the draft next year if he comes out.
As for other teams, it's mixed. I don't think Michigan misses Gary at all, I didn't notice when he did or didn't play this year. Higdon is the big loss, particularly with Samuels getting booted off the team last week. Evans is not an every down back.