So what is a 2-gap 4-3 anyway?
 

Fact: The Pats played a lot of 4-3 in preseason
Fact: The Pats played a lot of 4-3 in their first Super Bowl run, and some subsequently
Fact: BB insists it always has been a 2-gap defense

Guess: In a 2-gap 4-3, DTs line up over OGs, and DEs over OTs. The strong-side OLB lines up over the TE, jamming him if he tries to go out for a pass or, if he doesn't, treating him as a blocker the same way the DL do the OL. The ILB shares responsibility with the DTs for the gaps to either side of the C -- and by the way, in most cases the C will double on one of the DTs. The weak-side OLB -- uh, he reads the play and does what's needed, or else he takes the job of somebody who's stunting/blitzing, or else he rushes the passer himself.

How am I doing?

Re: So what is a 2-gap 4-3 anyway?
 

It essentially means your DL need a high level of alertness as their responsibilities are tougher.

Looked like Ten was 1-gapping last night. And it was BAD news.

Re: So what is a 2-gap 4-3 anyway?
 

Actually during the run game, where gap control makes the biggest difference, they looked great. The problems they had was that they couldn't get pressure with just four people rushing, that is when they looked terrible.

SSDD

Re: So what is a 2-gap 4-3 anyway?
 

Yeah, I thought the run d was stellar, too. It just seemed like they didn't shake it up at the end when they needed it most. Felt like I was watching Pats/Jets 2.0 from last year.

Re: So what is a 2-gap 4-3 anyway?
 

A 43 is (dependent upon scheme) is traditionally broken down this way from the linebackers down to the d-line:

Will Mike Sam.

RE T T LE

The autoformat on the site won't allow me to diagram the spacing, but essentially envision the set as follows: The right end is aligned on the outside shoulder of the left tackle. The right defensive tackle is aligned in the left side a gap, left defensive tackle is aligned in the right side a gap. The left end is aligned on the outside shoulder of the right tackle. Above that, the Will (denoting weakside) linebacker is aligned three yards deep head up on the weakside tackle. The Mike (denoting middle) linebacker is aligned three yards deep head up on the center. The Sam (yes, of course) linebacker is aligned three yards deep head up on the strongside tackle. I should add here that these sets can and frequently do change. For our purposes though, I am using as vanilla an explanation as possible.

From there, assuming a run play, the tackles have gap responsibility. In a two gap, they will try to occupy both the a gap and their shaded lineman. The mike is usually assigned the center as the primary defeat, with the fullback and/or downblocking linemen as the secondary defeat to the football. It is critical to understand that playing linebacker against the run is fundamentally about flow to the football, in addition to backside contain. On an a gap run, the Mike needs to fill the hole, ideally shedding the fullback and making the play, but more practically stoning the momentum of the fullback and sealing the hole; forcing a cutback or bounce out. On a b or c gap run, the Sam (and rarely Will) has responsibilities very similar to that of a traditional 34 OLB. They need to seal the second level seam of the blocking scheme and allow the scraping Mike or crashing SS to finish the play, depending upon play designation. Due to the splits of the 43 ends, they must maintain outside leverage at all times, and prevent the play from extending past their outside shoulders. They must fight to prevent the tackles, (and likely downblocking TE or cracking Y) from washing them at the POA. If they accomplish their responsibility by either turning the play inside by eliminating the outside angle, or stringing the play outside to allow the flow of the Sam to reach the football, they are doing their job as a 2-gap end. The backside run responsibilities typically rely upon the Will. The Will in the 43 must be aware of the reverse, the counter, or other misdirection type plays. Their primary responsibility as the backside defender is to prevent a backside cut back from forming. Once that option has been negated, it is on the Will to drive hard laterally to the football. Should the weakside toss present itself, the Will must drive hard to the D gap and attempt to break the play up in the backfield either by blowing up the pulling guard or fullback and enabling the free to make the play, or by making a sure tackle on the unguarded tailback. Due to the nature of these responsibilites, the Will is typically your fastest linebacker. Guyton is an obvious fit at this spot, and will in my opinion be an exceptional one.

There's literally dozens of pages I could write about the various responsibilities, but this is a very high level view 101.

Re: So what is a 2-gap 4-3 anyway?
 

Wrap "code" tags around it. That should make it doable.

Re: So what is a 2-gap 4-3 anyway?
 

Help me out, correct what I get incorrect here-


I always understood that head up wasn't used as often in the 4-3?

If the defender is attacking the linemen and the gap isn't that a single gap, and a two (jam) gap when only attacking the linemen?

Another thing I have noticed is that sometimes we are not running a 4-3, but are in the 3-4 with the stud coming in when facing a single TE and it appears to a lot of people we are in the 4-3.

What is strange to me is that our schedule this year has some decent passing offenses against us, but everyone feels this defense is getting geared and personnel for the 4-3. While both formations and disguises are effective, don't you think the 3-4 will serve us better against the spreads and the air attacks?

Re: So what is a 2-gap 4-3 anyway?
 

That is the basic idea. The weakside OLB is responsible for the gap on either side of the blocker that shows up (ie pulling G or FB) just as he is in the 34.
There are variations. It is common to play one of the DTs over the C and offset the MLB. (In this case you have the equivalent of a 34 with one ILB as a DT over the G instead of up over the G)(ps that is why we are more likely to run a 34 because the 4th rusher shouldnt be Mike Wright or Ron Brace it should be AD)
Really the best way to visualize the difference is this:
Move the "Xs"
NT becomes MLB
ILBs become DTs.
Everyone else is aligned the same. (Again note the variation above)

So what that means is our base 34 turned into a 43 means we bring in Brace and take out Guyton (or if you prefer Woods and put Guyton in Woods spot, which btw failed last year)
The 7 various 2 gap responsibilities are unchanged, and the 4 outside players are aligned the same.

Inside its either 2 Dts and 1 LB or vice versa.

Some will say changing to a 43 would entail not bringing in a DT but a DE, essentially just replacing Woods with Burgess.
However there is a lot more happening than that.
First we have created a mismatch in run D shifting from a 300lb Warren on the T to a 260lb Burgess struggling to 2gap. Its possible that G to G is strengthened (but thats debatable) but run D isnt about the part of the los you are strongest its about where you are weakest.

The biggest dilemma is the pass rush.
Assuming a front 7 in a 34 of Warren-Wilfork-Wright-AD-Mayo-Guyton-Woods and one in a 43 that adds Burgess and removes Woods.
Your 5 rushers are Warren, Wright, Wilfork all slowed by playing 2 gap discipline all doing the exact same thing AND
Burgess in a 43---aligned on the T, playing 2gap--engage the blocker---discipline.
AD (or Woods or even an ILB) in a 34---standing up, seeing the play, reading playaction on the move instead of while engaged, and rushing the QB.
That difference IMO is monumental and why the 2gap is not often played in a 43.

Re: So what is a 2-gap 4-3 anyway?
 

Basically, one gap means you are only responsible for that one gap, penetrate through it. 2 gap means you are responsble for the gap on eihter side of the guy across from you. The post above is incorrect about alingment on outside shoulder for that reason. You give an unnecessary disadvantage to covering half of your area by shading to the outside of the man.
I think we don't defend spread offenses much from the base, but from the nickel.
By my impression (didnt stop to analyze) we never play base against the Colts we play nickel. In one of the Colt games (I think it was 06) we played, for the first time I'd seen it a 3-3 nickel as the base and removed an OLB rather than an ILB. Had to be something in film study but the weak ILB (where there was no olb) would move outside at the snap (I cant tell whether it was a call or based on a read) to account for the weakside run, which the Colts did a lot of.

The primary difference to me is that the dilemma in a 2 gap D is getting a pass rush, particularly on play action. The 43 inhibits it, and the 34 helps it.
If we really are going to play 43, I will be very concerned about playaction on early downs which is something we always have a hard time defending due to scheme and would be even more susceptible to in a 43

Re: So what is a 2-gap 4-3 anyway?
 

You have alignment problems.
On the strongside you have no one responsible for contain outside the TE.
You have a DE out of position to 2gap, but account for that by giving the OLB his duties.
On the weakside you have no contain once a G is pull or a FB leads, and again have the OLB redunantly aligned.
Correct alignment to 2 gap has to be headup or you create a disadvantage.
You have to account for 7 areas to 2 gap.
Basically, you take your 34 alignment and turn the "X" that is NT into MLB and the ones that are ILBs into DTs.