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.  

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 (match zones, especially quarters—but other things as well). It's definitely Staley part II—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" 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 to two-gap it 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 (either one-gap or two-gap) or a 4-3. But playing a gap-and-a-half a team can play with six players in the box rather than seven if they choose. 

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 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"
Certainly, the defense would run stuff the run in the middle holes if it is run there but if the gap-and-a-half does not get good penetration, as it often does not, the runner has to find a gap outside of the B-gaps is a good thing. 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 effective two-gap if he is head up, push the center back and read the flow, as is seen above. However, he has help from the B-gap players who are playing their gap, plus trying to squeeze the gap next to them, covering half the gap with the body of the guard. If not head up then he plays the gap-and-a-half technique, gets in the gap, wraps his arm around the blocker to leverage half of the gap next to him. Essentially it is getting enough penetration in their assigned gap and shrinking their secondary gap (the half-gap) by pushing or "squeezing" on it if there is a cutback by the runner.

Now, on different alignments there are different assignments, the nose tackle might have a gap-and-a-half rather than playing head up and reading two gaps. The best way to tell is how a player's technique shows up on the video, two-gap looks distinct and so does gap-and-a-half, as does one-gap. So there is even some differences play to play depending on the call on a specific play.

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.

As with all defenses, there are, of course, variations and wrinkles. The defensive coordinator can slant the line, effectively making it a one-gap. And many times, due to his tremendous skill set, Aaron Donald will 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. 

Then, "gap-and-a-half" is somewhere between the two, asking a player to take a gap but not penetrate 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. The light box worked well but also this year and last year the Rams mixed in one- and two-gap with the gap-and-a-half and sometimes even employed a gap-and-a-half in a 3-4 (normal box), not just in the light box.

In 2021, under Morris, it has not been as good as it was in 2020—not in the run, 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 a quarters, quarters match, soft zone team, or will also play single-high off-man coverages as well. They did last year and this year as well, play Tampa-2 in the red zone.

Here are some recent examples of the fronts we've outlined all from the Lions game last Sunday—
Gap-and-a-half out of a 3-4

One-gap out of a 3-4

Two-gap out of a 3-4

Gap-and-half out of the 5-1 (33 nickel)
A further explanation of the coverages would probably be in order at some point, but that is a discussion for another day. But in general, the Rams show a Cover-2 shell almost all the time. They will rotate one of the safeties into the middle for a single-high robber coverage (to try and thwart in cutting routes like digs and posts). Or they will play a lot of match quarters or even cover-6 as well as others. 

Neither last year nor this year have they played much aggressive man coverage—it does not work with this scheme. The idea is that teams are not going to be able to consistently have long drives and that it is better to play that way than give up big plays by playing man coverage and giving up chunk play after chunk play, especially in the seams where teams get burned. 

If they wanted to play aggressive man coverage (which few teams use much of) they could simply junk the gap-and-a-half and play a 4-3, wreck havoc and get into the backfield and really help the DBs because you cannot play light box light the Rams do and also play aggressive coverage, it does not fit very well. Fronts and pass rush are always tied to the coverages called.

For the last two years with the light box TITE fronts and they have played mostly soft coverages and relied on the defensive backs to make great breaks on the ball and challenge receptions when the ball arrives and in 2020 they were tremendous at it. This year they have not had quite the success they did in 2020 but they are getting better at it. 

Why the dropoff? It is speculation but video study gives us the view that LS Jordan Fuller is not yet to the John Johnson III level—it took Johnson a couple years to get to the All-Pro level (One of our Second-team All-Pro safeties in 2020).  And RS Taylor Rapp is not where Fuller was (a top rookie in '20) at that position last year. The Rams also lost Troy Hill, and the "next man" up is not quite to the level he was and so on down the line. 

The same is true for the defensive line and possibly linebackers, too. However, it is set in Jello right now because we have not yet hit the midpoint of the 17-game 2021 season.

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.


  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.