Football coaches have developed many defensive strategies over the decades. These strategies, designed to stop an opponent from moving the ball and eventually scoring, are based on a variety of formations that place defensive players in certain positions on the field and assigning them responsibilities, such as rushing the passer or covering a tight end on a pass pattern. Each of these formations inherently possesses strengths and weaknesses.
4-3 Defensive Formation
The 4-3 formation places four defensive linemen on the line of scrimmage. That means they are lined up right along the ball before the center snaps it. They face the opposing team’s offensive linemen. Behind the four linemen, three linebackers position themselves to cover receivers, blitz into the backfield of the offense or tackle running backs carrying the ball after a hand-off.
The 4-3 is strong against a running play because four larger defensive linemen are close to the offensive backfield, and they can clog up running lanes. The formation is weaker against a passing play because fewer linebackers in the zone beyond the line of scrimmage are available to cover receivers, such as tight ends or running backs coming out into the pass pattern.
3-4 Defensive Formation
The 3-4 formation places three linemen on the line of scrimmage and four linebackers in the area behind those linemen. The 3-4 faces more challenges stopping the run because linebackers are quicker and smaller than the linemen, who also have just three players to match up head-to-head against up to five offensive linemen in this formation.
The 3-4 is a flexible pass defense, though, because four capable pass defenders can confuse the offense by blitzing through the line or from the edges of the blocking schemes as soon as the ball is snapped. That will force the quarterback to rush his throws. The blitzes also will force the offense to choose whether to keep a tight end or running back in to block instead of sending him out on a pass pattern.
Football teams employ a “nickel” formation to stop an offensive play that is highly likely to be a passing play. A basic defensive formation uses a combination of seven linemen and linebackers and four defensive backs. The nickel adds a fifth defensive back to the formation, ending up with a 4-2-5 or 3-3-5 formation. The faster defensive backs are better at covering pass patterns and match up against offenses that send five or six receivers on pass routes. This usually occurs when the team on offense is trailing and needs to move the ball in a hurry with passes while trying to catch up.
The nickel defensive formation is vulnerable to running plays because it doesn’t place as many players near the line of scrimmage, and the smaller defensive backs usually aren’t as strong at tackling as linebackers and linemen.
Coaches often use a mix of standard formations, depending on the game situation or a unique offensive scheme that an opponent uses. A team that runs a shotgun-based “spread” offense and places a heavy emphasis on its passing attack would be countered by a defensive formation that could use up to six defensive backs, while using only three linemen and two linebackers, for example.
Also, a team that is on the 1-yard line with the ball or faced with a short-yardage situation anywhere else on the field might bring in extra tight ends to place as blockers on the line to squeeze ahead on a running play and gain that yardage. The defense would counter with a larger ratio of players on the defensive line. Each of these defensive formations are specialized -- strong in one facet but vulnerable in another.