LeBeau's system commonly calls upon linemen to be mobile enough to drop back into zone coverage in place of blitzing linebackers. Elements of the 3–4 zone blitz defense have been incorporated over time into the modern Phillips 3–4.
In LeBeau's system, defensive linemen are often required to be flexible and retreat into zone coverage when linebackers blitz. As a result, elements from the classic 3–4 zone blitz defense have evolved and been incorporated into the modern Phillips 3–4 scheme.