This article serves as a primer on understanding pass defenses in the NFL. Familiarity with the concepts here will help you identify these coverages, but more importantly their strengths and weaknesses to better understand why an offense might use them in a certain situation.
To break things down into manageable chunks, topics are organized as follows:
- Basic positions in pass defense – Describes defensive positions and the roles they may fill
- Base and “sub” defenses – Examines base defense and “sub” defenses and when they are deployed
- Man and zone coverages – A tutorial on man and zone defenses and the advantages and disadvantages of each
- One-deep safety shells – Explains Cover 1, Cover 3, and other one-high safety shells
- Two-deep safety shells – Discussion of Cover 2 (both zone and man varieties), Cover 4, and other two-safety shells
- Other – Alternative defense shells
Basic positions in pass defense
To start, understanding pass defenses requires knowing there are eleven players for each team. Only the five eligible receivers need to be covered. Typically these are offensive “skill” players – any combination of running backs, wide receivers and tight ends. Basic defenses generally use four pass rushers who engage the offensive linemen and try to sack the QB. That usually leaves seven defenders to cover the eligible receivers. Below are descriptions of the defensive positions and their roles in pass defense:
The three or four members of the defensive line, stationed along the line of scrimmage, will typically rush the quarterback in passing situations. In rare instances, they may be asked to drop into coverage, usually a shallow zone, in an effort to deceive the offense through surprise.
The two, three, or four linebackers (so named because they play “back” of the defensive line) are set up in a rough box ranging from the line of scrimmage to a few yards behind the D-Line, and extending laterally a few yards outside the linemen in either direction. Linebackers will typically cover underneath zones, though the middle linebacker may take a deep zone in a “Tampa 2” defense (discussed below). In man coverage, linebackers most frequently cover running backs and tight ends, though they may also cover slot or wide receivers at times. Linebackers also commonly rush the quarterback, especially in 3-4 defenses.
Cornerbacks typically defend wide receivers, lining up across from them in man or zone defenses. On rare occasions they may defend other types of receivers or be called upon to blitz. A slot corner or nickel back (often called a “star” in the Patriots defense) is a third corner who defends a “slot receiver,” one who lines up between the outside receiver and offensive tackle. Because the slot corner sets up more towards the middle of the field, he has some linebacker-like responsibilities in a zone defense or in run support. A sixth defensive back is called a dime back (“money” in the Patriots defense) and has a similar role to the nickel corner.
In defenses with only one deep safety (see below) the free safety most commonly fills that role. He is usually not responsible for an individual player, instead covering a deep zone even in most man-coverage defenses. In such situations, he provides help for any underneath defenders needing it. He might “shade” closer to a dangerous receiver before the play begins, or he might see a corner is beaten and move to intercept the receiver and/or the throw. He’s also the last line of defense tackling downfield; if he misses a tackle, the consequence is often a long touchdown. In situations with two deep safeties, he plays a similar deep role, but only covers half of the field.
The strong safety has perhaps the least-defined role in the pass defense; he’s often a “Swiss army knife” that can perform many functions. He might play a deep zone (like the free safety) in a two-deep safety set. He might match up on a tight end or other receiver in man coverage. He might play an underneath “robber” zone even in man defensive sets, lurking to disrupt routes crossing the middle of the field. He might play a linebacker-type role in run support or even blitz. For more information on these positions, see the descriptions of individual coverage shells.
Base and “sub” defenses
Base and “sub” are designations that describe the composition of defensive personnel (as listed above). By rule, if the offense substitutes, the defense is allowed the opportunity to do so as well. In general, defenses “match” offensive personnel – two cornerbacks will defend two wide receivers, and a third receiver demands a third corner in response. Some situations are more ambiguous, such as a two tight-end set where one of the tight ends has elite receiving skills. That forces the defense to make a decision as to whether to use another defensive back to cover that tight end or another linebacker for run defense. Playing too “light” (too many defensive backs) will make the defense vulnerable to the running game, while playing too “heavy” exposes it to the pass.
Base defenses have four defensive backs (almost always, two safeties and two cornerbacks) and a combination of defensive linemen and linebackers to fill the other seven positions. The most common configurations of “front seven” players are the 4-3 (four down linemen, three linebackers) and the 3-4 (three linemen and four linebackers). Since this defense only features two cornerbacks, teams commonly deploy it only when the opposing offense has two receivers – for instance, in 12 or 21 personnel.
When faced with more than two receivers, defenses typically substitute (hence “sub defense”) a slot corner (see above section on “Cornerbacks”) for a linebacker. This most common sub defense is called the nickel, and the slot corner is often called a “nickel back.” A slot corner is better able to cover a third receiver, so this matches up better against 11 personnel, or 12 personnel where one of the tight ends is a dynamic receiving threat. The modern NFL is much more pass-heavy than it has been historically, and teams often find themselves in sub defense 50-70 percent of the time.
A dime defense has one more substitution than the nickel, swapping a second linebacker out for a sixth defensive back or “dime back.” With only five players in the defensive front, the dime is light against the run, so this is typically only used to match up with offensive personnel of four receivers and/or zero running backs (such as 10, 02, or 01 personnel) or in situations that force the offense to pass (late in the half, or 3rd and long). It is rare, but teams sometimes will substitute a seventh defensive back in “prevent” situations where they have a large lead late in the game.
Near the goal line, offenses will often remove wide receivers in favor of jumbo packages featuring multiple running backs and tight ends (such as 22 or 23 personnel). The defense will substitute players to match; if the offense has no wide receivers on the field, it is common to see a defense with six linemen, four linebackers, and only one defensive back.
Man and zone coverages
This is straight-forward – each pass defender will be assigned an offensive player to cover. He will line up across from that player and follow him anywhere on the field. In press coverage he will play on the line of scrimmage and attempt to jam or re-route him – basically, hitting him – in order to disrupt the receiver’s route before it begins. This can upset the designed timing of the play. Such contact is only legal within five yards of the line of scrimmage (the so-called “chuck zone”). In off man, the pass defender will line up anywhere from 2 to 12 yards away from the receiver, depending on the situation and play call, and attempt to mirror his actions and stick with him in space. In modern defenses, teams have code words that allow defensive players to “pass off” assignments to each other, incorporating zone concepts to disrupt route combinations designed to defeat man coverage. For example, if the receivers cross paths, thereby creating a natural “pick,” the defenders might switch rather than stay with their initial men.
Defenders are assigned to an area of the field rather than a specific opponent and are expected to cover pass defenders who run through the area. Zone defenses are considered “safer” because they are less vulnerable to individual lapses, but they are susceptible to short completions. There are also pockets of empty space or “seams” between zones that offenses can exploit. Zones tend to be stronger against the run since it is easier for zone defenders to look into the backfield, whereas man defenders must keep track of their assigned receiver. In modern defenses, especially in the Bill Belichick/Nick Saban coaching tree, zone defenders are often encouraged to read keys and “look for work” (by aggressively covering players in their zone), thus incorporating some man concepts into the zone defense. The zone assigned to a player can be of various depths. “Deep zones” are far from the line of scrimmage, typically 15-20 yards off, and the player assigned to the deep zone is responsible for making sure no one gets past him downfield. “Underneath” zones are closer to the line of scrimmage, typically 5-15 yards off. The “flats” are wide zones extending all the way to the sideline and up to 10 yards from the line of scrimmage.
In Cover 1, also known as “man-free,” the free safety plays a deep zone in the middle of the field. The cornerbacks and underneath defenders play man-to-man coverage. With five man defenders and the free safety – assuming a four-man rush – the defense has an extra unassigned man. That player (usually a linebacker or strong safety) can blitz the quarterback, “bracket” (double-team) a dangerous middle-of-the-field receiver, or play a “robber” role by lurking in an underneath zone and reading the quarterback. Cover 1 defenses can be vulnerable to big plays if they don’t have a free safety with a lot of range along with good man coverage cornerbacks and linebackers. Even for teams that play a lot of zone, Cover 1 is a common third-down defense, as the reward (forcing a punt with a stop) outweighs the risk (giving up a big play).
On the surface, Cover 3 looks like Cover 1; there are corners on the outside, a free safety in the deep middle, and the strong safety and linebackers underneath. But while Cover 1 is a man-to-man defense, Cover 3 is a zone defense. The cornerbacks are responsible for the WRs all along the sideline, including deep, but they have safety help to the inside if a receiver runs an in-cut or cross. The linebackers and strong safety play zone coverage underneath. Cover 3 has the benefits of a zone defense – with three deep defenders, it’s not vulnerable to the big play, it puts a safety in the box to help guard against the run, and the underneath zones protect against crossing routes that can stymie man coverage. Moreover, the outside corners play man-to-man against many of the routes, so it’s stouter against short receiving routes than most zone defenses. This combination has made it popular in recent years, most recently when the Seahawks rode a modified Cover 3 to the Super Bowl XLVIII Championship.
This is a zone defense where the two deep safeties each occupy one deep half of the field’s width. The cornerbacks cover a flat or curl zone underneath, with the linebackers occupying underneath zones. The safeties don’t need as much range as in one-deep safety sets, since each only covers his half of the deep zone. The corners don’t need as much speed either, since they aren’t responsible for deep men. They do have to be strong tacklers and stout run defenders given that both safeties play deep and are subsequently not well positioned to help against the run. The Cover 2 defense has fallen out of favor in recent years, as modern offenses are savvy enough to attack the “seams” between the zones or overload the deep safeties by sending multiple receivers into one zone.
The “Tampa 2” defense (so named because it rose to prominence in the 1990’s under Buccaneers head coach Tony Dungy and defensive coordinator Monty Kiffin) divides the deep part of the field in thirds, with a middle linebacker dropping back to cover the deep middle. This eliminates some of the seams in the zones, but requires a linebacker with safety-like speed.
Sometimes called “2-Man” or “Cover 5,” this is a defense where the two safeties split the deep part of the field (as in Cover 2), but the linebackers and corners all match up in man coverage. It is less susceptible to deep attacks than Cover 1, but because there’s no extra underneath defender it can be vulnerable to outside runs. Since the man defenders usually play “trail” technique in this set (following behind the receivers, since they have help in front), they’re facing away from the line of scrimmage with their backs turned.
Cover 4 or “quarters” has four deep defenders, but rather than a strict zone like Cover 2 they play something of a man/zone hybrid. The cornerbacks cover the full length of the sidelines, while the safeties handle the two deep zones in the middle. Like Cover 3, the corners have help inside – from linebackers for short routes and safeties deep – but the corner effectively plays a lot of man concepts. With four deep men, the Cover 4 is a safe coverage, but with only three underneath defenders it is vulnerable to runs and short passes.
This is a variant of Cover 3 where the three deep zones are not evenly divided. Instead, one of the safeties covers half the field deep (as in Cover 2) while the other safety and one of the cornerbacks combine to cover the other half of the field (as in Cover 4). If the ball is snapped near one of the hash marks rather than the center of the field, the safety who has to cover his half alone will handle the narrower “boundary” side. The other safety and corner take the wider “field” side. This coverage is more common in college ball, in part because college fields have wider hash marks.
In Cover 0, there are no safeties deep. This is normally an entirely man-to-man coverage that involves a heavy pass rush (six or seven rushers). Teams often use Cover 0 in goal-line situations, where there is no deep field to defend. It is rare in other situations, as the risk of giving up a big play is great with no safeties deep. Follow Dave on Twitter @.
Dave Archibald knows pass defense, specifically how coverage, the pass rush, excellent cornerbacks, versatile safeties and in-game adjustments can make a big difference.
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