Since College Football is now professional football we are starting to see talent be spread out across teams and conferences. Back in Bo's time in Ann Arbor, he would just sign a 100+ really good players. When one went down, another would step up. The same thing could be said about Alabama or Georgia. They would load up rosters so the next man up would be just as good or better then the player that started and got injured.
Now rosters are skinny and lack depth even for those two SEC giants. Any team can lose any Saturday.