Depth and guys who can play multiple positions are needed for any system, as there are only so many roster spots. Again, this is ultimately a FO (talent) and coaching( making the most of said talent). My position is not so much that injuries are irrelevant, just that good organizations can overcome injuries and retain a level of completeness.
IMO, KKs system is highly likely that the backups will have significant platying time. Unlike our previous system that just required an Olineman to hold up a few seconds pass blocking.