‘Crucial, vital, essential, necessary are just a few of the words that describe indispensable. Buffalo’s defense has made some critical additions that should raise the level of play on that side of the ball. Their depth is also appreciably better in some areas, but injuries have compromised promising Bills’ seasons before. And as hard as GM Buddy Nix has tried to make his roster complete there are still a few areas where if a starter goes down it will be hard to maintain the same level of play. Here are the candidates on defense that the Bills can least afford to lose.’