Running the ball is much easier said than done. Coaches at every level talk about the importance of running the ball, but frequently end up in charge of teams where they, for example, throw the ball 47 times with a 2nd round rookie quarterback who clearly isn’t ready to carry such a load. Why? You’ve probably heard the phrase “run to daylight,” but in the NFL there typically isn’t a lot of “daylight” available. If you really want to commit to the run, sometimes you have to run it despite “darkness.”
Simple arithmetic tells us that if the defense has more players in the box than the offense has blockers, the defense has an extra man to tackle the ball carrier.