In order of importance:
Ralph Wilson,Buddy Nix,Chan Gailey,the players on the field led by the QB.
Wilson is responsible for hiring Nix to bring in quality players, Gailey is responsible for properly coaching the players and selecting the proper plays, and finally the players are responsible for executing the plays led by the QB (as the most important player).
If the players aren't capable, then ask yourself, "Who hired them?"