It is more about depth. We have been scary thin with quality players at these positions over the last decade. We might have had a couple of quality D1 guys but once those guys went down there was a sever drop off at talent. What makes the top teams great is that they can run the second team on the field and you would never notice the drop in play. Been the case going back to DM's days.
Another issue we have had is the staff want the kids in the program to have the schemes down pat, there is a huge drop off when the "next man up" from your starter is a freshman who is just learning the ropes compared to a kid who has been in the program and is challenging the starter for reps.
The staff is also making transitions to the type of player they want/need to compete in this conference. Taller WR, quicker LB's, bigger CB's, etc... Our starters are more in the mold of what we want, athletes athletes athletes. Many of these players can be shifted just about anywhere as we saw this week.