Generally, we speak about defenses and coverages as if there is a uniform language. In actuality, it’s as if the football gods scattered defensive coaches through languages as punishment for building their own Tower of Babel.

Coaches often convene in clinics or privately to help each other improve in the offseason, but there can be confusion and breakdowns in communication when talking about defense. One coach from the Nick Saban tree can talk about a certain coverage to a coach from the Rex Ryan tree and both coaches could be talking about two different coverages and they might not even realize it until they’re halfway through the conversation. The language of offenses is a little more straightforward and uniform, but defensively there are inconsistencies and nuance.

Do you necessarily have to know all the different languages to talk about football on a high level? No, but it could be beneficial to acknowledge the differences to recognize when there might be a breakdown in communication and try to bridge the gap. For coaches, this could cut down on misunderstandings. For fans and media, especially those who are curious about schemes, this could help us elevate the conversation.

One principle that extends to every defensive tree is that coverages are numbered from one to nine. There are a few coverages that we can generally talk about, and it would be safe to assume that we’re talking about the same coverage yet there can even be some nuance within those coverages.

Before we begin, I want to acknowledge Brian Vaughn of Blitzology.com, who is a human football encyclopedia when it comes to defenses. Most of this information stems from my conversation with Vaughn and confirmed through looking at various playbooks.

Coverages

This next section will break down each coverage by numbers and show the differences of each number in different systems. It can be a little confusing, so don’t fret if you don’t get it on your first read. The point is this: One type of coverage can be numbered the same but be an entirely different coverage in different systems.

Cover 0

When most people talk about Cover 0, they’re talking about man-to-man coverage with no deep help, and it’s usually called with a heavy-pressure scheme.

This diagram is from Pete Carroll’s 2013 playbook. The “0” at the end of “Coast Tuff Saw Dog 0” indicates the coverage is Cover 0.

However, to Saban and company, Cover 0 is actually man-free (man coverage with a deep safety) with no underneath help from a “hole” player. It’s usually called with a five- to six-man pressure.

In this diagram from Saban’s 2015 playbook, the call is “Even $ 0 Change.” The “0” indicates that the coverage is Cover 0. The money linebacker ($) and free safety blitz, leaving no hole player. The strong safety rotates to the middle of the field and plays deep.

Cover 1

Cover 1, Cover 2 and Cover 3 are universal terms. Cover 1 is man-to-man coverage with deep help from a free safety and underneath help from the “hole” player, with a four-man rush. However, there are many Cover 1 variations and some differences in terminology for the “hole player.”

When a linebacker is a hole player, he’s generally called the “rat.” When a safety is the hole player, he’s generally called a “robber.” Even with this simple concept, there can be a ton of variance with terminology from system to system. The term “robber” can be extremely problematic in football discussions because it has so many varying definitions across the different systems.

This diagram is from Wade Phillips’ 2003 playbook. The “Mo,” his terminology for a weakside linebacker, is the hole player.

The principles within Cover 1 can also completely change with a tag. For example, coach Bill Belichick and the Patriots made “1 double (jersey number)” famous. So whenever they wanted to double a certain player, they would insert their jersey number in the call. So if they wanted to double Randy Moss (No. 84), they would call “1 double 84.” It was essentially Cover 1 because it’s man-to-man coverage with a deep safety, but instead of having a hole player, they would use the extra player on a double team.

This diagram from Romeo Crennel’s playbook shows the free safety and star (*), which is their terminology for a nickelback, doubling the slot receiver.

Cover 2

Cover 2 is a two-deep zone with five underneath defenders, usually with two deep safeties and two corners in the flats.

Variations of it include “2-invert,” in which the corner would play a deep zone and the safety plays underneath.

Cover 3

Cover 3 is a three-deep zone with four underneath defenders, usually with both corners and a free safety playing deep thirds.

Variations of it include “3-roll,” in which the corner would play in the flats while the coverage would roll to his side to cover each third.

Saban’s “Cora” coverage is an example of 3-roll. The safeties drop to the deep thirds of the field while the corner to the twins side plays the flat.

Cover 4

After Cover 3, things start to get tricky. Cover 4 is commonly used as an umbrella term for all the different variants of quarters coverage. But the technique and responsibilities within different quarter coverages can vary greatly.

This diagram is from former Raiders defensive coordinator Paul Guenther’s playbook. “Under” is the front, “Red” indicates that this is a red-zone defense and “44” indicates that they’ll be in Cover 4 against all formations (we’ll talk more about the double-digit call system later in this article). On the diagram to the right is Guenther’s Cover 4 adjustment against slot formations.

In Phillips’ system, however, Cover 4 is quarter on one side of the field and Cover 2 on the other.

Cover 5

Most know Cover 5 as “2-man,” which is man-to-man coverage with two deep safeties and no underneath help. The man-to-man defenders will usually play with inside leverage and trail technique (purposely play man underneath assignments to be in a better position to take away short and intermediate routes).

However, in the system of Baylor coach Dave Aranda, who has been highly influential in modern defense, Cover 5 is quarters with eight defenders in coverage and a three-man rush.

Cover 6

Generally, Cover 6 is a combo coverage in which one side of the field plays quarters or Cover 4 to the strongside and Cover 2 to the weakside. Within this coverage can be a ton of variance because of all of the different types of quarters and Cover 2.

On the left of this diagram from Guenther’s playbook is a standard Cover 6 look against a pro formation with a receiver on each side of the formation. On the right is his standard adjustment to a slot formation.

In Saban’s system, Cover 6 is weak rotated Cover 3 with man-match technique. Man-match coverages are coverages in which defenders play man but can switch assignments after the snap if their original assignment runs a certain type of route.

In this diagram, the free safety rotates down to the weakside (away from the tight end) and the strong safety rotates into the middle of the field.

Cover 7

In Saban’s system, Cover 7 is a family of man-match coverages but from two-deep alignment instead of one-deep like his Cover 6.

Cover 7 has split field coverages, meaning the defense can play different coverages on both sides of the field. In the diagram, “7 bracket” is the coverage. Against this formation, the defense plays a “bracket” to the two-receiver side and “cut,” which is Cover 2, to the tight end side.

In other systems, Cover 7 could be quarters variants that may not use man-match techniques. The Saban definition of Cover 7 is not as universal as many may believe.

Cover 8

In Phillips’ system, Cover 8 is quarters on both sides of the field, but in Vic Fangio’s system, Cover 8 is what is generally known as Cover 6, with Cover 2 to the strongside and Cover 4 to the weakside.

In Saban’s system, Cover 8 is a family of zone-match coverages in which defenders are assigned zone but locks into man coverage once an eligible receiver runs a route into their zone.

Cover 9

Cover 9 has vastly varying meanings in different systems. It could be a Cover 1 principle type of defense, a robber principle or fire zone (blitz coverage).

Coverages within the coverage trees

Within each of these coverage trees are variants. Some variants are similar to each other, like within the Cover 3 family is 3-roll. But there are some coverages that can greatly differ from each other within the same family. For example, within the Cover 7 family is “bracket” (diagramed above) and another type of man-match defense generally known as “2-read.” A “2-read” on a two-receiver side in Saban terminology is called “clamp.”

Diagram above from Saban’s playbook

This same coverage in TCU coach Gary Patterson’s system is called “blue.”

And if that isn’t confusing enough, although “clamp” and “blue” share the same principles, the techniques and methods that each coach teaches the coverage can greatly vary. So even when talking about a coverage as specific as 2-read, you have to differentiate how you play it, Saban style or Patterson style. The alignment, read and assignment can greatly vary in 2-read.

How coverages are called

Coaches build their coverages around numbers. So why is it that some coaches will call out double digits in their play call? The two numbers could indicate different things in different systems. In most NFL systems, the two digits might indicate two different coverages. The first digit tells the defense to play a coverage against pro formations and the second digit tells them to play another type of coverage against slot formations.

Oddly enough, some NFL defensive coordinators have to make it a point to teach defensive rookies what slot and pro formations are because they just don’t see a lot of them in college with all the spread that they face in college.

Pro formation:

Slot formation:

For example, if the call is “63,” the defense plays Cover 6 against pro formations and Cover 3 to the weakside of the formation. This numbering system was originally intended to defend mainly two-back sets. However, it still works in the modern game by just switching out formation types for spread ones. So instead of the first number indicating what coverage to play against pro formations, it would be for two-by-two formations. Slot formations would be swapped out for three-by-one formations.

In this page from a Jets playbook or install, the call is “Reduce 63.” “Reduce” is the front and “63” is the two coverages. The two diagrams on the left show that the defense would play Cover 6 against pro and trip formations. The two diagrams on the right show that they would play Cover 3 against slot and twin formations.

The reason why calling two coverages is necessary is because the type of stress one set of formations deals with can be completely different than the type of stress that another set of formations can put on a defense. With pro formations or two-by-two formations, the offense is more balanced with two receivers on both sides of the field, but there are some formations that present very specific stresses on a defense that require a different call or adjustment.

For example, against a three-by-one formation with a nub tight end (inline tight end on the single side), the running strength (to the tight end side) is the offense’s run strength and the passing strength is to the three-receiver side. That type of conflict requires the defense to have an adjustment or different coverage against those types of formations.

This article reveals merely the tip of the iceberg when it comes to how the languages of defensive football vary. Hopefully, by the end of this, you realize that we all don’t know as much about defenses as we think we know.

When it comes to analyzing schemes, speaking about defensive football as if there are universal terms is totally incorrect. If I claim that a cornerback was guilty of a blown coverage, I wouldn’t know for sure unless I knew the defensive call, which I wouldn’t get a majority of the time. But to make the best-educated guess possible, I would have to investigate details like what coverage he was in, what tree is his coach from and more. I am certainly guilty of oversimplifying, but as an analyst in the media that is presenting my work to football fans with a wide range of football expertise, this vice is often necessary. The aim is to keep learning, be as accurate as possible and keep elevating the general conversion around the game we love.

(Photo of Vic Fangio holding a play sheet: Justin Edmonds / Getty Images)