Gap Exchange between Defensive Linemen, Linebackers, and Safeties
Gap exchange in defensive football occurs between defensive linemen, linebackers and safeties is a critical element for many over fronts and under fronts.
Gap Exchange: Block Down Step Down
The basic gap exchange concept begins at the defensive linemen level, where the defensive linemen responds to a down block by an offensive linemen or tight end. The linemen is likely taught the theory of block down step down, where if the linemen blocks inside he must step inside, disrupt said linemens path, and spill kickout blocks.
The linemen, given the block down step down rule, cannot play his original gap. In essense, he is playing his immediate inside gap. He needs to also focus on getting hands on the blocker who stepped inside while keeping his shoulders square. The defensive linemen simply needs to give a push with one hand, enough to keep the linemen off the playside linebacker or knock his path on his way to a backside linebacker. The defensive linemen, be it end or tackle, must focus, at this point in the play, at keeping his shoulders square. Turning his shoulders this close or on the defense’s side of the line of scrimmage will make it easy for another linemen to log him or, depending on the play, to get around him completely without making the blocker take a better pull path.
Gap Exchange: Open / Closed Window
The linebacker needs to read the open or closed window. This should be an easy read as the linebacker flows to his gap. An open window essentially means that the gap he is assigned to his open. A closed window means the gap is blocked and the runningback will not see that hole.
Why is this important to gap exchange principles? As the linebacker reads his hole, if for some reason the defensive linemen is in his gap (he got washed down, or even a called stunt—which means a predetermined gap exchange), then the linebacker needs to work one outside gap, or to the next open gap and press the line of scrimmage while keeping his shoulders square. By pressing the line of scrimmage right away, this causes problems for offensive plays like power where the kickout and wrapping pull blocker occur quickly.
Gap Exchange: Secondary Run Support
In many cases, a safety or even a corner, depending on the defense and the formation, may be called upon to gap exchange with a defensive end or EMOLOS. This is common in the Under front, where the Sam linebacker, lined up in a 9 technique outside the offensive tight end, must follow block down step down principles. In this case, the safety must be ready to come up quickly and exchange gap responsibilities with the Sam linebacker.
Gap Exchange – Conclusion
Overall, gap exchange is a good way for a defense to take advantage of the spill technique and use the sideline and team speed to its advantage. If the team has good speed and the front 7 have great hip explosion to help execute some of the technique (wrong arming or spilling), then this can be a great asset for undersized defenses.
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