When I watch film of other teams or watch football on the weekends, I notice a common factor of successful teams.. EXECUTION. There are many defensive and offensive schemes in the game of football and people have won a lot of games with different schemes. The scheme is not important, but the EXECUTION of the scheme is of paramount importance. It does not matter how many different schemes a coach can draw up on a board or put in a PowerPoint, what matters is the ability of his players to execute their assignments on every play. Now, you need to have some versatility in your package, but NEVER sacrifice EXECUTION for a larger playbook.
Steven R. Covey says, "You have to decide what your highest priorities are and have the courage to say no to other things. And the way you do that is by having a bigger 'yes' burning inside."
If more football coaches listened to that statement, more people would have successful seasons. In order to be successful, you have to coach what you know. It is better to be excellent at a few things than be a jack of all trades and a master of none. Your players will always know less than you, so you must be an expert on your scheme. If you are not an expert; do some research, talk to other coaches, go to clinics, so you can become an expert on your scheme. If you are going to demand that your players EXECUTE their job to perfection, you better know your scheme inside and out, so you can prepare them for the different situations they will face.