Eric Kasperowicz, Mars HS (PA), Head Coach
Full video on Glazier Drive: Run Fits in the 4-3 Dynamic Defense System
This article was originally posted on the Glazier Coaching Blog.
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DEFENSIVE RUN FIT FUNDAMENTALS IN 4-3 SYSTEM
This transcript covers essential run-stopping responsibilities and techniques for each position in a 4-3 defensive scheme, emphasizing the importance of sound gap assignments and disciplined execution.
DEFENSIVE LINE PHILOSOPHY
The base approach is a “box” scheme where defensive ends force everything back inside while defensive tackles spill plays outside. Defensive linemen must get vertical and attack in relation to their key (the outside shoulder of their alignment technique), not just mindlessly rush upfield. Ends play C or D gaps, while tackles handle A or B gaps depending on their alignment. The core technique is “two to one” – strike with two hands, then press off with one while keeping the outside arm and leg free to maintain leverage.
LINEBACKER RESPONSIBILITIES
Linebackers are run-first players who attack on fast flow reads. Outside backers must understand “apex” positioning – getting wide enough to reroute receivers but tight enough to fulfill gap responsibilities. They need to master block destruction against spread offenses where receivers regularly block in space. One outside backer will always have an internal gap unless the scheme dictates otherwise.
CORNERBACK ASSIGNMENTS
The best cornerback goes to the boundary side where offenses typically isolate their top receiver. While corners aren’t immediate run players, they must show courage in crack-replace situations and be capable of filling when receivers block the force player. They should give the illusion of press coverage while maintaining flexibility to bail, play cover two, or blitz.
SAFETY RESPONSIBILITIES
Safeties are the critical “plus one” defender who makes everything work. They need exceptional eye discipline to avoid offensive window dressing like motion and play action. Their coverage zone begins at the “hard deck” (five yards from scrimmage) – anything below belongs to underneath defenders. Against trips formations, they cross-read number three, taking him vertical or becoming a “robber” to provide extra run support. The best safety goes to the field side to handle multiple vertical threats. When there’s no immediate pass threat, they must aggressively attack the run.