Defensive strategy
Thursday, November 24th, 2005Defensive strategy
The general goal of defensive strategy is to prevent the opposing team’s offense from scoring. While doing so, the defensive players may also attempt to gain control of the football and score points themselves. There are many different defensive strategies.
3-4
The 3-4 defense declined in popularity over the years, but has found renewed use by modern professional and college football teams. The 3-4 defense is so named because it involves 3 down linemen and 4 linebackers. There are usually 4 defensive backs.
The 3 down linemen attempt to break into the backfield in order to sack or rush the quarterback or to stop running backs and other players behind the line of scrimmage. The defensive line is made up of a nose tackle (NT), who lines up in front of the opposing team’s center and two defensive ends (DEs), who flank the nose tackle on both sides. Linemen in 3-4 schemes tend to be more massive than their 4-3 counterparts to take up more space and guard more territory along the defensive front.
4 linebackers line up behind the defensive line. In a 3-4 defense, the linebacker unit is made up of two middle or inside linebackers (MLBs/ILBs), who are flanked on both sides by outside linebackers (OLBs).
The strength of the 3-4 is its ability by its design to confuse the quarterback during passing plays. Most teams generate a pass rush by sending at least 4 defensive men at the quarterback. In a standard 4-3 alignment, these 4 rushers are usually the 4 down linemen. But in a 3-4, the fourth rusher is a linebacker. Since there are 4 linebackers, the fourth potential rusher can come from a variety of spots on the field, thus influencing and sometimes confusing the quarterback’s pre-snap defensive read.
A drawback of the 3-4 is that without a fourth lineman to take on the offensive blockers and close the running lane, both the defensive linemen and the linebackers can be overwhelmed by blocking schemes in the running game. 3-4 linebackers must be very athletic and strong enough to shed blocks by fullbacks, tight ends, and offensive linemen to get to the running back.
4-3
The 4-3 defense is probably the most commonly used defense in modern American Football. The 4-3 defense is so named because it involves 4 down linemen and 3 linebackers. There are usually also 4 defensive backs.
The defensive line is made up of two defensive tackles (DTs) and two defensive ends (DEs). The two defensive tackles line up in the middle of the line, in front of the opposing team’s center. The two defensive ends flank the defensive tackles. DEs in 4-3 schemes are usually smaller and quicker than their 3-4 counterparts since the fourth lineman provides additional leverage to close running lanes. These smaller DEs allow defenses to collapse the quarterback pocket quickly, at worst disturbing his timing and at best causing a fumble, sack, or interception.
3 linebackers line up behind the defensive line. In a 4-3 defense, the linebacker unit is made up of a middle or inside linebacker (MLB/ILB) code-named Mike, who is flanked by the weakside (Will) and strongside (Sam) linebackers.
The 4-3 is widely used because of its balance in stopping both runs and passes as well as being personnel-friendly since smaller players can be used effectively along the defensive line.
Nickel
The nickel defense is employed in obvious passing situations, or against a team that frequently uses four-wide receiver sets on offense. The defense has 5 defensive backs, and has either 4 down linemen and 2 linebackers or 3 down linemen and 3 linebackers.
In most defenses, the secondary consists of two cornerbacks (CBs), a free safety (FS) and a strong safety (SS). The nickel defense adds an extra defensive back, known as the “nickel back” (NB), in order to defend against the pass. A nickel back is also employed in the “dime” defense (see below) and are usually free or strong safeties, although cornerbacks can be utilized as well. The term “nickel” comes from the five-cent value of a United States nickel, in reference to the fifth defensive back.
Dime
The dime defense is usually employed in obvious passing situations. The formation usually consists of 6 defensive backs, and has either 4 down linemen and 1 linebacker, or 3 down linemen and 2 linebackers.
A dime defense differs from the nickel in that it adds yet another defensive back to the secondary. The sixth defensive back is called a “dime back” (DB). The defense gets its name because a dime is two nickels.
Quarter
The Quarter defense has 3 down linemen, one linebacker, and 7 defensive backs. This is usually only used in a third-and-very-long situation (because the defense can afford to allow a short gain), to prevent a long score on the last play of a half, or when the defense believes that the offense will definitely pass (for example if the offense goes into the huddle without anyone competent to carry the ball). This gets its name because the defensive backs divide the field into four vertical quarters for zone coverage.
Half-dollar defenses, with eight defensive backs, are very rare and are often used to prevent a Hail Mary pass.
Eight in the box
The defensive linemen and linebackers collectively - or, more properly, the area of the field where they typically line up - are often referred to as “the box” and thus normally number seven players; on occasion, however, circumstances call for an additional man to be placed therein (generally a linebacker if the team uses the 4-3 as its base alignment, or a defensive lineman in cases where the 3-4 is ordinarily utilized), whereupon one player in the secondary (most commonly the free safety) is removed from the lineup. Sometimes a player in the secondary (usually the strong safety) acts as an additional linebacker and no actual lineup change ensues. Some teams use a defensive system in which one of the players is cross between a linebacker and a strong safety and is called a “rover”.
Teams most often put “eight in the box” or “stack the box” when the opposing team has a strong running game. By having more players closer to the line of scrimmage the defense can more effectively contain the opposing team’s running game.
46/Bear
A variation of “8 in the box” in the NFL is called the 46 or “Bear” defense. It is designed to put pressure on the QB by lining up the defense with 3 defensive linemen covering the center & guards, and the 4th defensive linemen lined up either “wide” outside the TE or wide off the weak-side Tackle. The linebackers & strong safety are lined up behind the defensive line to put pressure on the QB as well.
Coverage Shells
In the following, “cover” refers to the “shell” that the defense rolls into after the snap of the ball, more specifically the numer of defenders guarding the deep portion of the field.
Cover 2
In traditional Cover 2 schemes the free safety (FS) and strong safety (SS) have deep responsibilities, each guarding half of the field.
Cover 2 can be run from any number of defensive fronts such as the 46, the 3-4, and the 4-3. Various “underneath” coverage played by cornerbacks and linebackers may also be implemented. For example, Cover 2 Man means 2 safeties have deep responsibility while the cornerbacks and linebackers follow their offensive assignment in one-on-one coverage. Cover 2 can also be paired with underneath zone schemes: Cover 2 Zone refers to 2 safeties with deep responsibility but now the CBs and LBs drop back into specific coverage zones where they defend passes ONLY in their assigned area.
Teams that play Cover 2 shells usually ascribe to the “bend-but-don’t-break” philosophy, preferring to keep offensive players in front of them for short gains while limiting long passes. This is in stark contrast to a more aggressive Cover 1 type scheme which leaves the offensive team’s wide receivers in single man-to-man coverage with only one deep helper. By splitting the deep field between two defenders, the defensive can drastically reduce the number of long gains.
The main weakness of the Cover 2 shell occurs in the middle of the field between the safeties. The safeties attempt to gain width upon the snap of the ball to cover any long passes to quick wide receivers down the sideline. This movement creates a natural hole between the safeties that can be attacked. By sending a receiver (usually a tight end) into the hole, the offense forces the safety to make a decision: play the vulnerable hole in the middle of the field or help out on the wide receiver. The quarterback reads the safety’s decision and decides on the best matchup (which mismatch is better–TE vs S or WR vs CB).
Cover 1
Cover 1 schemes employ only one deep defender, usually a safety. Many underneath coverages paired with Cover 1 shells are strictly man-to-man with LBs and defensive backs each assigned a different offensive player to cover. By using only one deep defender in Cover 1, the other deep defender is free to blitz the quarterback or provide man-to-man pass coverage help.
Cover 1 schemes are usually very aggressive, preferring to proactively disrupt the offense by giving the quarterback little time to make a decision while collapsing the pocket quickly. This is the main advantage of Cover 1 schemes–the ability to blitz from various pre-snap formations while engaging in complex man-to-man coverage schemes post-snap. For example, a safety may blitz while a CB is locked in man coverage with a WR. Or the CB may blitz with the safety rotating into man coverage on the WR post-snap.
The main weakness of Cover 1 schemes is the lone deep defender that must cover a large amount of field and provide help on any deep threats. Offenses can attack Cover 1 schemes with a vertical stretch by sending two receivers on deep routes, provided that the quarterback has enough time to for his receivers to get open. The deep defender must decide which receiver to help out on, leaving the other in man coverage which may be a mismatch.
A secondary weakness is by its design: the use of man coverage opens up yards after catch lanes. Man coverage is attacked by offenses in various ways that try to isolate their best athletes on defenders by passing them the ball quickly before the defender can react or designing plays that clear defenders from certain areas thus opening yards after catch lanes.
Cover 3
Cover 3 refers to 3 deep defenders each guarding one-third of the deep zone. Cover 3 schemes are usually used to defend against passes, mainly those towards the deep middle of the field. Unlike Cover 2 schemes that create a natually hole between safeties, Cover 3’s extra deep defender is able to patrol the middle area effectively.
The most basic Cover 3 scheme involves 2 CBs and a safety. Upon snap, the CBs work for depth, backpedaling into their assigned zone. One safety moves toward the center of the field. The other safety is free to rotate into the flat area (about 2-4 yards beyond the line of scrimmage), provide pass coverage help, or blitz.
As with other coverage shells, Cover 3 is paired with underneath man or zone coverage in its most basic form.
The main weakness of Cover 3 shells is the 2 retreating CBs. Since the CBs are working for depth, short pass routes underneath the CB can isolate him on a wide receiver near the sideline with little help.
Cover 4
Cover 4 refers to 4 deep defenders each guarding one-fourth of the deep zone. Cover 4 schemes are usually used to defend against deep passes.
The most basic Cover 4 scheme involves 2 CBs and 2 safeties. Upon snap, the CBs work for depth, backpedaling into their assigned zone. Both safeties backpedal towards their assigned zone.
As with other coverage shells, Cover 4 is paired with underneath man or zone coverage in its most basic form.
The main weakness of Cover 4 shells is the retreating defensive backs. Since the DBs are working for depth, short pass routes underneath can isolate them on a wide receiver near the sideline with little help.
Cover 0
Cover 0 refers to pure man coverage with no deep defender. Similar to Cover 1, Cover 0 has the same strengths and weaknesses.
Tampa 2
Tampa 2 refers to a style of defense played by Tampa Bay and implemented by its coaches in recent years. It differes from Cover 3 in that instead of dropping defensive backs in deep coverage, it drops the Mike, or middle linebacker.