The two basic defensive schemes are the 4-3 and the 3-4 defenses. The following list will break down each defensive scheme that team uses and the personnel that makes the defense work or, in some cases, not work.

There are two main defensive schemes in the NFL. These defensive schemes are defined by their front 7 alignment as either a 4-3 defense or a 3-4 defense. Within each scheme there are variations, such as 1-gap or 2-gap principles, or Cover 2/Tampa 2 zone secondaries.

This series focuses on the responsibilities for each of the following defenses: The one-gap Phillips style 3-4, the two-gap Parcells style 3-4, the LeBeau "Blitzburgh" 3-4, the one-gap 4-3 defense like what Mike Zimmer uses, the two gap 4-3 defense like what Jack Del Rio uses, the Jim Johnson style 4-3 defense, the Rex Ryan 34/43 hybrid, and the nickel-and-dime defensive packages.