The two main defensive alignments used by all NFL (and college) teams are the 4-3 and the 3-4 defenses. The 4-3 defense has four down linemen and three linebackers while the 3-4 defense has the opposite, three down linemen with four linebackers. In both of these formations it is assumed that there are two cornerbacks and two safeties. As the names imply, these defensive alignments only refer to the numbers of linemen and linebackers and therefore do not refer to what kind of pass coverage a team may be in. Both defenses can use zones, man-to-man coverage or a mix of both as suits their own needs. While coaches like Bill Belichick of the New England Patriots will often try to confuse the offense by switching into more exotic alignments, the majority of all offensive snaps that take place in the league are facing one of these two main formations.
The 4-3 Defense
The 4-3 defense is the most prevalent defensive arrangement currently used in football. The four down linemen (“down linemen” refers to a player on the line of scrimmage who is starting from the 3-point stance, a crouch like position, leaning forward with one hand on the ground) take the responsibility of rushing the quarterback and stopping the run. Generally speaking, the defensive ends are quicker and take on a larger portion of the role of pressuring the quarterback, while the interior linemen (the defensive tackles) are generally larger men who are primarily responsible for stopping runs up the middle. However, all four of the linemen will work together and share both jobs. With four men on the line, ideally a team will not have to blitz to create pressure, leaving the three linebackers to assist in pass coverage and shutting down the running game as needed.
The 3-4 Defense
While the 4-3 defense is the standby for all teams in the league, teams with the right personnel will often opt for the 3-4 defense, which is by nature slightly more confusing to the offense. Here, the three down linemen consist of two defensive ends and a nose tackle. The nose tackle is a hard position to fill, as it requires a player of enormous strength, size and ability. He will often face at least two offensive linemen and is responsible for the entire center of the defensive line of scrimmage. The three linemen are first and foremost responsible with stopping the run. With only three men on the line, there is an extra player standing up and moving around the field. This extra linebacker can be used to blitz from any side to pressure the quarterback or can be used as an extra pass defender. It is this extra bit of flexibility that makes the 3-4 defense more aggressive and bewildering.
While the 4-3 formation is more common in today’s NFL, both alignments have been proven to be effective. In choosing which formation to use, it boils down to two factors: the philosophy of the coach and the defensive personnel your team has. If your team has an abundance of linebackers, or undersized but fast and rangy defensive ends, it may be best to be in a 3-4 formation to take advantage of the athleticism and versatility that your players have. In addition, a 3-4 defense will need a true stalwart at nose tackle, a player that can dominate the center of the line. If you have more classic defensive ends – combination players who can pass rush and stuff the run, who are both quick and strong – or you are short on linebackers and speedy large players, your team is probably more suited to the classic 4-3. As mentioned, there are other formations that are used – anything and everything from no down lineman to five or six – but these two are the mainstays of every team.
With the 2007 NFL season quickly approaching its beginning, everybody needs to brush up on their football knowledge. Check out the rest of my “Understanding the NFL” series to read up on topics such as the Cover 2 defense and much, much more.