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Today, most defensive coordinators will tell you they’re a spill team. That means they want to keep the ball going from side to side and prevent it from cutting down the field.
Each defense also uses the principle of a “holding player”. The containing player is the player who stops the spill. In our 4-3 Defense, we say that everyone on the defensive front is spill players, and one player (on each side) is the “box” player.
The box player simply boxes the play and forces it back inside. That’s in a perfect world, of course.
Many coaches use the term “Force” the player instead of “Contain” or “Box” because they want the player to force the ball to change direction in some way. Either the ball carrier needs to turn inside, where the help is, or they need to bubble the ball to try to get around the forced player.
If the ball carrier is forced back, that gives the inside chase a chance to get there. It also means the player is closer to pinning down the sideline. The sideline is the 12th man in any football defense.
The 4-3 Defense is a true spill defense. Each player on defensive front 7 is responsible for the inside half of his allotted space. He should almost collide with the blocker who is within his gap responsibility.
We call this “squeezing the air” out of space. Think of when you put something in a ziplock bag and squeeze out all the air before sealing it. By removing all space between him and the inside player in space, the ball is forced, at worst, to continue out of him.
As players squeeze the air in the 4-3 Defense, we’re building a wall of defenders for the ball carrier to maneuver. There should be no place for him to go up the field. Even the slightest crease can result in a mess. It only takes one player to be unable to squeeze the air out and we could be in trouble.
If each player does their job building the wall, the ball will continue out of the spill and eventually collide with the containing player or box player. The box player in our defense is usually the Strong Safety or Free Safety on the play side. We used quarter coverage to engage both safeties on the run defense and create a 9-man front.
The final piece of the puzzle is the deep defenders. If we use quarter coverage, we have a 9-man front and two defenders who should always be above the #4 receivers. #1. These are the corners.
You can’t count on any defender who is responsible for a deep zone of the field, or who is locked in man-to-man coverage, for his running attacks. He is not in the spill, nor is he the box player. Our cornerbacks have the job of eliminating deceptive passes, game actions and other plays where wide receivers could pose a threat even after the offense gets going.