Friday, October 29, 2021

One, One-and-a-Half, and Two-Gap—A Simplified Explanation

 By John Turney 
Last year we mentioned Brandon Staley's "gap-and-a-half" front but we never really gave an explanation as to what it is. So in this post, we will give the basics. The more complicated part of it we will leave to those better qualified.

In 1983 the Rams switched from being a 4-3 to a 3-4, but it was a two-gap 3-4, unlike many today which are hybrid schemes, they may be a 3-4 base defense but they are not doing as much one-gapping. For example, Wade Phillips ran a one-gap 3-4 most of his career and did so with the Rams from 2017-2019.

Then in 2020, Brandon Staley brought in some college concepts that allowed for run stopping-of played properly but allows for more people in coverage because they can run a lighter box, 6 players rather than seven. It's called different things we'll use Fangio's term of  "Penny front" (personnel is 33 nickel) but when they line up it looks like a 5-1 with the ends in two-point stances. To make it work, since they are short in the box the front three have to cover all the interior gaps and the outside linebackers set edges.

In 2021 Raheem Morris is doing the same things, using the same scheme but like Staley did in 2020 he mixes in 3-4 one-gap and 3-4 two-gap and sometimes some 4-3 concepts as well but the "go-to" front is usually the 5-1. Morris is also using the same coverages and fronts. It's Staley Part II with perhaps some tweaking by Morris. Rams head coach Sean McVay hired Morris to take over Staley's playbook and replicate what Staley did so well in 2020.

So, in that the two 3-techniques (players aligned one on the outside shoulder of the guard or 4i (4 inside) techniques are in the inside shoulder the offensive tackle. This makes the front "TITE" or as it is sometimes called "MINT" by some coaches or even a "Bear" even though a Bear front is two 3-techniques and this is two 4i techniques or maybe a 3-technique and one 4i technique. 

These two players, call them the 4i-techs, have to control the B-gaps but also "squeeze" the A-gaps to help the nose tackle who is head up on the center and has either A-gap at times, making the so-called gap-and-a half a hybrid scheme. 

So here is a very basic rundown of the schemes.

So, here is how a two-gap scheme works—
The players long up head up on their players, the ends in a 4-technique (head up on a tackle) and 0-technique which is head up on the center.  

The way Fritz Shurmur, Bill Parcells, and the other two two-gap schemes had their guys play was as follows: At the snap of the ball explode into their player and push him back, and read the play. If the flow goes to your right, play the gap to your right. If the flow goes to the left, play the gap to your left.
The linebackers flow to the ball, reading the same flow and their keys.

In Wade Phillips' version of the 3-4 everyone including the linebackers had a gap—

Ideally, the edge to the play side will turn backflow (set the edge with penetration to proper depth), the backside edge will have cutbacks, bootlegs, and reverses (CBR), the playside tackle will penetrate and disrupt the play, hoping to make the tackle, the backside tackle will do the same but also wait for the cutback. The backers will fill their gaps looking to make the tackle in the ball carrier shows in their gap. The theory is to wreck the play by filling all the gaps. It does not mean that happens with every gap every play—the offensive linemen get paid, too but that is the idea, penetrate and disrupt.

Really, it is a pass rush and if pass shows the linebackers will drop to their zones (or cover their man).   

In this system, the run defense is designed to clog the middle and bounce runs to the outside where the linebacker and safety rotating down make plays on the ball carrier. The defense wants to make a pile in the middle with fewer people handling the gaps than does a 3-4 or a 4-3. But playing a gap-and-a-half a team can play with six players in the box rather than seven. 

Staley's defense last year and this year with the Chargers and Morris' this year do that with a Penny/5-1 look that has three linemen in the TITE/TUFF front and two linebackers on the edge of the line of scrimmage and one linebacker on the second level. The personnel 33 nickel but when you look at it it could be described as a 5-1 with 5 on the line and 1 MIKE backer. 
One example of the 5-1 or "Penny"
The defense wants to stuff runs but with gap-and-a-half penetration (not as far as a one-gap scheme). If done right inside runs are stopped or the runner has to find a gap outside of the B-gaps (bounce) and that is a good thing, too. The edge players should get penetration (wall off outside runs) and it is still close enough for the MIKE of the left- or right-safety to get there, depending on who is rotating down.

The idea is to have the nose if he is head up and get to his primary gap, one of the A-gaps depending on the call. However, he has help from the B-gap players who are playing their gap, plus trying to squeeze the gap next to them -- their secondary gap, covering half the gap with the body of the guard or just popping over to make a play. You can see this in film, they kind of "peek" looking for the ball carrier. 

Essentially it is getting enough penetration in their assigned gap and reading then squeezing/shrinking or stepping into their secondary gap (the half-gap). It's having the linemen overlap assignments so fewer plays can cover the same amount of gaps.

In a sense, they are making a pile of sorts that a back cannot get through. They cause a back to "bounce" because of that pile and because of the technique, they can leverage their off-hand and move a blocker enough to disengage and make a play.
Gap-and-a-half assignments, NT can have a call play side, backside or a choice
As with all defenses, there are, of course, variations and wrinkles. The defensive coordinator can slant the line or one of the linemen, effectively making it a one-gap. And many times, due to his tremendous skill set, Aaron Donald appears to freelance and get penetration as he did under the 4-3 from 2014-16 and the one-gap 3-4 from 2017-19.

He's too good of a defensive weapon to have him push a guard around. He can do it, but what makes Donald rare is that he can push a guard if needed, but can also beat him with a fast charge into a guy with a swim, a rip or just getting his head in front of the guard. Or, if the guard gets a good jump Donald can backdoor it and still make a play chasing it. It would be a waste if the Rams didn't give Donald the green light to do that when he sees something he likes.

It is a football axiom "If you can do it, do it" meaning if you need to break the scheme you can do it as long as you make the play. If not, you play the scheme the coach's way.

In a way, it is like the national campaign slogan "If You See Something, Say Something" which raises public awareness of the indicators of terrorism-related crime or even crime in general. With Donald, if he sees something he can DO something to stop the offensive play. 
And as we mentioned there are many more components we just are not familiar with that someone else can explain but fans should know "two-gap" means "one-gap" right after the snap of the ball. If flow goes on way, then that is the gap you fill, the way of the flow. 

Presnap one gap gives the player knowledge of where he is going and uses quickness to fill the gap, but also if he beats the blocker gets into the backfield and really mucks things up for the offense. among other things penetration kills outside zone plays.

Then, "gap-and-a-half" is somewhere between the two, asking a player to take a gap but not penetrate deeply but squeezing a gap next to him and this allows for a "light box" (six rather than seven players) and therefore if pass shows it gives an extra defender in coverage.

Since the Rams (and Broncos and Chargers and some others) play left- and right safeties rather than strong and free both have to be able to rotate down from the Cover-2 shell the Rams usually show and read and fill. That is one the lone MIKE 'backer does as well, though, on slants or other calls he can take a gap. 

Last year this defense worked as well as it possibly could with the Rams ranking at or near the top in the major defensive categories as well as both for the run and the pass. 

In 2021, under Morris, it has not been as good as it was in 2020—not in the run (that has been fine), not versus the pass, points allowed, pass rush but they have beaten teams that were in the playoffs last year and lost to a red-hot Kyler Murray Arizona Cardinal team and the defensive passer rating is 80.4, the same as it was for the 2020 season.

The coverages Morris is running are much the same, though Ramsey is playing in the slot more than last year, but also note that Ramsey didn't do it much early in the season. Perhaps Staley was getting the new scheme installed and making sure the players had it down pat before he started tweaking it. 

Later in the year, Ramsey was in the slot position "nickel" or "star" position, whatever one wants to call it a lot more. So the Rams still are Cover-2 shell but rotate into Cover-3, quarters (Cover-4 or a combination of Cover-4 and Cover-2 called Cover 6 or Cover 8.

They did last year and this year as well, play some Tampa-2 in the red zone -- as many teams do in that part of the field.

A further explanation of the coverages would probably be in order at some point, but that is a discussion for another day. 

There are ten games left and we have no idea if the 2021 defense will get better or worse or even stay the same under Morris, but it does seem this year's unit is picking up steam. We'll see if they can overcome some of the personnel losses from last year and start shutting down some of the good offenses they will face in the next couple of months.

If they do, and Matthew Stafford stays at his current level (near-MVP) they could do better in 2021 than 2020. But it is too early to tell. We'll see.


  1. ....this article is an excellent example of why folks should read the Pro Football Journal. how many researchers/historians have the knowledge and take the time to detail this fascinating/interesting aspect of run defense responsibility? Just one, Mr. John Turney.....superb job John. Could go hours on what you have above, and what an offense would literally "counter" with.

  2. Wow, this is INCREDIBLE content.