A recent book buyer told me his team ran the 7-3-1 defense. I called him and discussed it with him at length. I put the gist of the discussion and some of my related thoughts here so you can see how to think about defense.

Basically, he says they were quite successful with it. I thought it was unsound. He disagreed with my analysis. I still think I am right. If I am unable to convince you, and you know a high school or college coach, I suggest you show him this page and ask what he thinks.

Gap-air-mirror defense is a 7-3-1 versus a single wing

My defense, which I am now calling the gap-air-mirror defense, is actually in a 7-3-1 alignment when it aligns against a single-wing offense. That’s because the linebackers and dbs align in a way that more or less mirrors their offensive counterparts. The single wing stacks a bunch of offenders on one side, so the defense must do the same. That results in a 7-3-1.

5-1 at the C level

The team in question was at the C level, below A and B, in their league and they went 5-1 after they went to the 7-3-1. They never gave up more than two TDs and only gave that many up to a team that never scored that few in other games.

Stud safety

Actually, their safety sounds like he was an A-level player---extremely fast. He was on their team because he signed up after the teams had been chosen. Superior talent, especially speed, will enable a team to succeed with almost any defense. The youth football world is full of coaches who think their success proves that they are great coaches, but who are really successful only because of superior talent. They win in spite of their defensive scheme, not because of it.

Post hoc ergo propter hoc logic fallacy

This is a post hoc ergo propter hoc logic fallacy. That’s Latin. It means “after which, therefore because of which.” In this case the thought process would be,

“We ran the 7-3-1 defense. We won 5 of 6 games, therefore, the 7-3-1 defense was the reason we went 5-1 and it is a good defense.”

Or as it is usually phrased,

“Our record was _____, so we must be doing something right.”

which really translates to “Our record was _____, so most of the things we did were probably correct.” In fact, the truth may be that they went 5-1 in spite of their unsound defense and would have gone 6-0 had the run a gap-air-mirror. A winning record is not necessarily evidence of good coaching in all areas. A team may have a winning record in spite of poor coaching if it has superior talent, even weaker opposing coaches, or an extraordinary performance on one side of the ball or on special teams.


This 7-3-1 has a nose tackle, two tackles lined up in the B gaps (guard-tackle gaps), a defensive end lined up on the outside shoulder of the tight end, and a cornerback lined up on the line of scrimmage on the widest receiver or three yards outside if there is no wide receiver. There is a middle linebacker about two yards behind the nose and an outside linebacker stacked behind each of the defensive ends. And there is a safety about eight yards behind the middle linebacker.

Ever used before?

Has this ever been used before, like in the early days of this century? No. (The youth coach in question has since told me he got it from a high-school coach on the Internet at http://members.xoom.com/bcwarrior/Defense/wide7/wide7jumbo.gif. All I see at that Web page is a diagram of the defense against a double-tight-end power I.)

Does the fact that the defense has not been used before matter? Yes, it does. Generally, if a defense has never been used before, it does not work. If it worked, it almost certainly would have been used by someone. The seven-diamond was widely used. The best I can say for this youth 7-3-1 as far as having a proven history is concerned is that it is a sort of collapsed seven-diamond. The real seven-diamond is a 7-1-2-1, not a 7-3-1.

One nose versus two defensive guards

Is a nose tackle better than a defensive guard in each A gap, which is the gap-air-mirror configuration? The only reason to use a nose for both A gaps rather than a pair of offensive guards would be that you have an exceptional player for the nose position. He is covering two gaps and is therefore known as a two-gap player. Covering two gaps is extraordinary, therefore it requires an extraordinary athlete to play such a role. Furthermore, he cannot just be a generic good athlete. It only matters if he can do what a two-gap nose must do: control the center and prevent a ball carrier from coming through either A gap. If you do have such a player, it will free up a defender to strengthen another area.

The key to defensive guard play in the gap-air-mirror defense is staying real low. But a nose cannot play so low because he has to use his hands to control the center. I suspect he would be vulnerable to the blast play.

A nose can also be double-teamed for inside-trap plays. You cannot double-team block against a gap-air-mirror because there are not enough offensive linemen to cover all the defenders, let alone assign two offensive players to one defender.

Is a two-gap nose unsound in youth football? Yes, unless you have an extraordinary athlete playing the position and he can handle both gaps. In my experience, such an athlete comes along about once every two years. But I still never use a nose. I just make him a defensive lineman and do not coach him to stay low.

Nose-middle linebacker stack

Having both a nose and a middle linebacker enables the defense to slant charge the nose to one A gap and send the MLB through the other. The MLB would typically signal this to the nose by tapping him on one butt cheek or the other. I have no objection to the nose’s slant charge, but the MLB’s charge will be high and low man wins. A blast at the MLB’s gap should succeed unless he comes with enough force to knock the lead blocker backward at the hole.


The MLB could also loop through a B gap. In that case, you would have the B-gap tackle on that side loop through the adjacent A gap. Loops are good to confuse blocking assignments. The offensive linemen tend to make a quick read and conclude they have no one to block. Then the looping defender suddenly appears at full speed.

In youth football however, the offensive linemen do not need to be confused by the defenders. The offensive linemen in youth football have usually already been confused enough by their coaches or by lack of coaching. And any attempt to confuse the opponent runs the risk of confusing your own team. If you loop or slant varying directions, you will find your own players getting their signals crossed. Then you will have two or three guys going through one gap and one or two gaps totally uncovered.

Do not do such stunts in regular defense unless you are unable to have success with a straight gap-air-mirror. That should rarely be the case.

Defensive ends

The defensive ends lined up on the outside shoulder of the tight ends. On the snap, they bumped the ends then penetrated deep into the backfield to stop the sweep. In my experience, you cannot ask youth defensive ends to make any contact with the offensive linemen. If you do, they will get tangled up with the offensive lineman and be unable to contain the sweep. This coaching staff gave the defensive ends no pass responsibilities except rush. They also had no trail responsibilities.

Stacked outside linebackers

These are one of my biggest problems with the 7-3-1. These coaches stacked the outside linebackers behind the defensive ends, who are lined up on the outside shoulders of the tight ends. On every play, the outside linebackers charged through the C gap (tackle-tight end gap).

If you alternate the charges of the defensive end and the outside linebacker, as they do in the 4-4, you may confuse the offensive blocking. But these coaches did not alternate the charges. They always sent the outside backers though the C gap. In that case, I see no point to the stack. If the outside linebacker has C-gap responsibility and is supposed to charge through that gap on every play, he should be in a four-point stance in the gap. He should not commute to the gap upright.

The coach told me they stacked him to confuse the blockers.But I see no confusion after the first play or two if the backer makes the same charge on every play.

But the main problem I have with these stacked linebackers is that they have no pass responsibilities. Pass coverage is either zone or man-to-man. These linebackers are neither dropping into a zone nor do they have any man responsibilities. This is mathematically unsound.

The defense has five ineligible linemen and six eligible backs and ends. In the 7-3-1, we are already rushing our nose and two tackles. If we also rush the contain men, which we do in this defense, we are rushing five guys. To also rush the two outside linebackers give us a seven-man rush. Our rush should succeed, unless the offense is in a shotgun. However, that leaves only four defenders to cover five eligible receivers. Obviously we cannot cover them in man-to-man. We do not have enough.

Can we cover all the zones with just four guys? Maybe, when you consider that youth-football passers cannot throw very far. This was an 8-10-year-old team, the weakest-armed end of the youth spectrum. The zone-coverage pattern should probably be three linebackers and a safety. But that pattern is not available to us in the 7-3-1 as these guys ran it. Remember they crashed the outside linebackers into the C gap on every play. And they sometimes stunted the MLB.


This coaching staff had the cornerbacks line up three yards outside the defensive end on air if there was no wide receiver and on the wide receivers if there was. They were primarily contain men. They only had pass responsibilities if there was a wide receiver on their side. They were trail men on plays toward the other side.


The safety, therefore, was the only man who always had pass-coverage responsibilities. He was in zone and his zone was the entire field! Remember, the coach said he was really fast. He'd better be. He has to cover an area 55 yards across and up to 35 yards deep. In fact, it would be impossible for any safety to cover a zone this big, no matter how fast he was. This is unsound.

Strengths and weaknesses

This defense is great against the sweep. It has two contain men on each side. It should be great against the reverse as well for the same reason. Unfortunately, some “Peter” has to be robbed to pay “Paul” that much.

This defense is weak almost everywhere else. The blast should work. The sneak may depending upon the relative abilities of the center and nose. The inside trap should work because the nose can be double-teamed. If the trap is combined with misdirection, which is usually the case, the MLB will probably take a misstep or two in response to the initial flow of the offensive backfield.

The outside trap or counter should also work because the defensive end is taking himself out of the play or at least making it easy to trap him by overpenetrating. A wide off-tackle should work using a guard or fullback to kick out the defensive end who is overpenetrating. The tight end could block down on the outside backer. The offensive tackle could block down on the defensive tackle, with help from the offensive guard. The center stalemates the nose. If the defensive end overpenetrates, the pulling guard or fullback could ignore the end and block the MLB or corner, whomever is most dangerous.

The receivers can release inside because no one is assigned to prevent that. That opens the slant which is one of the easiest passes to complete. All out, fade, corner, and curl routes should be wide open. The safety should only be able to take away the post and maybe some hooks and deep crossing routes.

In an actual game, personnel strengths and weaknesses would prevent some things that theoretically ought to work from working. And some plays that should not work, like a B-gap dive with an option fake, may work. I did not discuss option defense with the coach.

High-school coach's version is sound

The 7-3-1 defense shown on the high school coach's page looks generally sound to me. (He calls it the "Wide 7.") In fact, it looks almost identical to the gap-8 except that the weakside defensive guard is dropped back off the line to become a middle linebacker. Also, he has cornerbacks covering tight ends in man, but switching to covering backs if they come out on a pass. I think that’s too complicated for kids. In the gap-8, the man you cover in case of a pass never changes no matter what the offense does (exception: crackback block by receiver against contain requires db and contain man to switch responsibilites).

He has strong safeties on the inside shoulder of each tight end. The corners are stacked behind them and are in man coverage on that tight end. All backs are covered in man by various defenders. The nose is a one-gap defender in the strong-side A gap and the MLB is over the weakside A gap. I think the defense is unsound for stopping a play through the uncovered A gap, but I suspect the high school coach would not use this defense in a short-yardage situation. The high school coach only has one contain man on each side, not two on each side. The high-school coach does not have anyone go through the C gaps. Apparently the strong safeties cover that gap after delaying any inside release by the tight end.

The high-school coach’s diagram shows both defensive contain men crashing at a steep angle into the backfield. I doubt that is precisely what the coach wants. The strongside end crashes inside the power back in the Web diagram. That would be unsound. The power back could eaily block the contain man in and the pitch sweep would be successful to that side. I suspect the coach actually tells his contain men to maintain outside “leverage” by attacking the outside shoulder of the potential backfield blockers with their inside arm and shoulder; never attack the inside shoulder of a potential blocker when you have contain responsibility.

The high school coach’s Web page is too brief to see how he handles all situations and formations or even what all the responsibilities are against the double-tight power I, but it seems generally sound as far as it goes. However, I still think the gap-air-mirror will give a much better result in youth football.

Conclusion about this 7-3-1 youth defense

In short, this youth 7-3-1 defense is unsound. It asks the one zone defender to cover too much ground in the event of a pass out of a double-tight-end formation. It makes man-to-man pass coverage, which is by far the best in youth football, impossible. It permits quick slant passes. The lessons coaches should learn from this discussion are that you must cover all the defensive threats to one degree or another. You cannot overemphasize any, even the sweep and the reverse, to the point where you ignore other plays. The other lesson is: do not invent a brand new defense. Find an old, proven one that fits your needs.

Good luck

John T. Reed