How to Choose a Base Defense in American Football
NFL coaches love to copy one another, primarily when a coach is successful with a particular offense or defense. For example, a lot of winning teams in the 1970s began to use the 3-4 defense (which uses three down linemen and four linebackers) as their base, or primary, defense.
The 3-4 was the defense of choice in the 1980s; only Dallas, Chicago, and Washington preferred a 4-3 scheme (four down linemen and three linebackers). By the time the 1990s came to a close, the 4-3 defense was back in vogue, thanks mostly to the success that Jimmy Johnson had with the Dallas Cowboys in the 1990s. In the 2014 season, a slight majority of NFL teams used some form of the 4-3 as their base defense.
Basically, what you need to understand is that the goals of any type of defense are to
Stop the opposition and get the ball back for the offense.
Seize possession of the ball via a turnover. A turnover occurs when the defense recovers a fumble or secures an interception.
To compete with sophisticated offenses, defenses have had to keep pace. In fact, some rules have changed simply to negate suffocating defenses. These rule changes have caused defensive coaches to return to the chalkboards and film rooms to devise more dastardly plans — and nowadays, they even use computers to uncover offensive tendencies.
Most defenses are named by their fronts, or the number of defensive linemen and linebackers who align in front of the defensive backs. The most common front is the front seven: four defensive linemen and three linebackers, or three defensive linemen and four linebackers. It’s assumed in football parlance that a front seven also includes four defensive backs: 7 + 4 = 11 players on the field.
Knowing why a team uses a specific strategy is important. Choosing a defense is like a game of checkers: A coach wants his team to stay a few offensive moves ahead of its opponent, anticipating the opponent’s next move or play.
The defense wants to prevent the offense from jumping over its defenders and reaching the end zone (or as they say in checkers, “King me!”). And, like checkers, you may sacrifice a piece in one area of the board (or field) to prevent the opponent from reaching your end of the board. The ultimate goal with any defense is to prevent a touchdown, so sometimes surrendering a field goal is a moral victory.