Just saying what Belichick said about execution:
For us, it's all about practice. Practice execution becomes game reality. If we can do it in practice, executing plays properly in practice in the right situation, then we have a chance to do that in the game. The players have done that before. They know what is expected. They know what the purpose of the play is and what the goal of the situation is, how to handle and what we're looking for as an end result. We try to execute the play properly in that way