Nobody has brought this up, and I would like to see some analysis on it, but I think what has lead to close games has been the number of series per drive. Meaning, it seems to me like time and again we find ourselves in 3rd and long situations, or at the very least, that we use every single down. Rarely can I remember us going from a first down, running a play, and getting another first down. That amount if time off the clock, with a high probability for the ball changing hands, will lead to close games.
to play football, not to play trumpet