Basic Defensive Coverages Series: Cover 1


For the next few weeks, we’re going to look at basic defensive coverage schemes and how the Buffalo Bills have used them. These will be 101-level introductions that just begin to hint at the schematic complexity NFL defenses employ against the best offenses in the league, but they’ll give you a leg up in trying to understand why a defensive back was in a particular part of the field or why that linebacker ended up covering a wide receiver.

Our first coverage scheme is Cover 1. We’ll break it down below, but let’s start with how the Bills utilize it.


According to Sports Info Solutions, the Bills used Cover 1 against 98 pass attempts, which ranked 25th in number of attempts. Don’t read too much into that specific number, because Cover 1 might have been the coverage called for a given play and the opposing offense ran, or there was a sack, or otherwise there wasn’t a pass attempt.

The Bills’ defensive statistics (and ranks) when using Cover 1 against pass attempts. This number from SIS may differ from what you might find elsewhere because it’s based on whether or not there was a pass attempt. For instance, if the offense used a running play while the Bills had set up in Cover 1, it would not show up here.

Introduction to How Cover 1 Works

There are three main types of Cover 1: 1 Hole, 1 Robber, and 1 Rat (Spy). For the purpose of brevity, the diagrams will include an offense in 11 personnel (1 RB, 1 TE) since that is a predominant grouping, and the defense will be in nickel (a fifth DB) since that it was the Bills ran about 94% of the time in 2022.

Cover 1 starts with the location of the safeties. Generally, the Free Safety will be deep in the middle of the alignment. This first version is One Hole. The Strong Safety will be in the box with a man coverage assignment. The 4 DL are rushing. The MLB’s responsibility is to cover a shallow zone in the middle of the field, up to around eight yards deep off the line of scrimmage. The other defenders are in man, playing with outside leverage because they have inside help from the MLB and FS.

For instance, if the slot WR runs a crossing route, the nickel CB will pass him off to the MLB once the WR has committed. The defender who has released his man to the inside help – the MLB in this version – now becomes the One Hole defender, potentially covering crossing routes from the other side.

To complicate matters, there will be rules where the crosser isn’t picked up by the hole defender, but we’ll leave that for the 200-level coursework.

Cover 1 is considered a Middle Of the Field Closed (MOFC) defense because the FS has “closed off” the middle of the field. For comparison, Cover 2, with its typical alignment of the safeties 10-15 yards deep, each on the hash marks with an opening between them, is considered a Middle of the Field Open (MOFO) scheme.

There should already be a number of potential variables occurring to you. The offense in this diagram is in 11 personnel, but what if they came out in 12, 22, or five wide? What if a RB like James Cook lines up or motions outside the numbers, would the WLB keep the same assignment or would the CB shift out to him? Responding to personnel and alignment changes is a crucial part of defensive pre-snap communication.

For instance, if the Y goes in motion to the right-hand part of the formation, there are two main ways for the defense to adjust from this scheme. First, the SS could travel with him, or the defense could shift the coverage responsibility across to the WLB, with the SS picking up the RB.

There are also variables for how the defense approaches the play. The defenders with man coverage responsibilities have two main ways of starting: press or off. There are two main types within press: jam or mirror. With a jam, the defender is trying to disrupt the receiver’s route and/or timing by pushing him immediately at the line of scrimmage. For mirror, the defender is attempting to match the receiver’s footwork and become a barrier to the route. These approaches are obviously available to the defender or defensive play caller outside of Cover 1 and are part of how defenses can present multiple styles from the same scheme.

1 Robber

Robber follows similar principles to One Hole, but the initial One Hole is deeper at 8-12 yards and the initial defender is the SS. At first look, this scheme looks like a version of Cover 2, with both S deep, and the middle of the field open (MOFO). At the snap, the SS rotates up and to the middle, while the FS drops back to range.

The rules are generally the same as One Hole. For example, if the Z WR runs a deep cross, the CB maintains outside leverage, and the SS picks the WR up coming into the middle of the field, robbing that opening. The CB who passed his man to the Robber, now becomes the hole help defender.

1 Rat or Spy

Cover 1 Rat closely resembles Mike Single, except instead of rushing the QB, the MLB mirrors his movements, prepared to attack if he decides to scramble.

Rat is still a four man rush with man coverage everywhere else.


These are Cover 1 coverages at their most basic, but how the more complicated versions build off of these fundamentals should be evident. Hopefully, you’ll be able to watch some of these basics take place on the field and have a deeper appreciation for the on-field machinations.

In the coming weeks, we’ll look at Cover 2, Cover 3, and Cover 4. We’ll also look at how some of those coverages are mixed together to create some of the more complex coverages.

You can find Chris on Twitter (@lowbuffa), getting dirty in #MafiaGardens, or watching football. Go Bills!