Demolishing Weakside Iso with the 4-3 Over Front


Often considered the longtime nemesis of the 4-3 over front is the weakside iso play. Because of the “large” gap between the outside linebacker and the inside linebacker, the play has some success.

The key to defending the weakside iso play with the 4-3 over front is the personnel matchup.

Many coaches, including myself for a while, always set the “Sam” to the tight end, regardless of whether or not they are in the 4-3 over front or under front. The Will played on the “weakside”.

The Will for many is an undersized player. Because of this, when he’s set over an open guard, he’s usually got a matchup problem, especially with a tough guard or fullback. This tends to happen on Weaskside Iso plays.

This article should give you an overview on how to stop the this often gut-wrenching play by thinking of your 4-3 defense a little differently in terms of identifying roles of your players and setting your strength.

A Background: Setting the Strength to get Matchups

Many teams, including the Chicago Bears under Lovie Smith, set the “Sam” linebacker to on the same side as the nose tackle and 5 technique defensive end. He does not necessarily play to the tight end.4-3 over versus 21p-

Many 4-3 defenses (and 3-4 defenses really) set the Sam and the Rover on opposite sides in almost every scenario. The Rover, basically a Strong Safety, plays on the same side as the 3 technique defensive tackle, 7 or 6 technique defensive end, and Will linebacker.

The nose tackle, Sam linebacker, and 5 technique end usually play on the same side.

The Mike and Free safety adjust a bit, but usually the Mike and Free are to the Sam linebacker side.

For many teams, the 3 technique side is considered the reduction. There are other ways to consider the Sam side, such as open or wide side.

Understanding the Matchups in the 4-3 Over Front

passing strength 4-3 under

Strengh is set to the passing strength, or pro side

Many teams will set the Sam to the passing strength, like in the Eagle defense. So, versus 21 personnel pro (I formation), you would have an under front. However, versus 21 personnel slot (I formation twins), the defense would give you an 4-3 over front.

passing strength 4-3 over

Strength is set to the passing strength, or twins side

While setting the strength is a little more complicated, it can be practiced and go fast. What this does drastically though is simplify technique and recycle it. For instance, many times the “Z” receiver will go to the passing strength, or a speedy slot receiver will. Scouting will help identify this.

However – you can simplify it by setting the strength to or away from the tight end. For this article, that’s what we’re going to do.To get our 4-3 over front look, we’d call “Open” for our front. This sets our strength Opposite the tight end. This will give us our classic 4-3 over front, except the Will is to the tight end, and the Sam is to the split end.

Now our Will linebacker is always protected. Offensive linemen hardly ever have a clear shot on him. The Mike has a similar surface no matter what.  This simplifies things for the two guys who should be making the most tackles.

The Sam Linebacker’s Role Versus the Weakside Iso Play

The big bonus, and the reason I mentioned all of this, is that the Sam linebacker is now one of two types of players.

He’s either a plugger with overwhelming strength and size, or he’s a nickel back wrestling type who can get to the point of attack quickly with good body control.

Many teams will use two different players for this role (one of each role described above), depending on the down and distance or formation grouping. For teams that have to use one player due to talent or less players on their team, that player is often more of the wrestler type if they have to pick between the two.

Regardless of what type of player you use, this player is built to take on fullbacks. What they’re really built to do is SPILL fullbacks.


This is where the teaching is recycled. When the defense is in an under front look (when he’s outside the tight end, on the LOS), the Sam will spill whenever he gets block down step down. When he’s in a 4-3 over front look, he will spill the fullback.


Now, you might ask why spill the fullback in the 4-3 over front? The next closest player is the safety, which might lead you to believe this is a bad idea.

North Carolina State’s (and former Wisconsin DC) Dave Doeren, would have the fullback get spilled by the Sam when he was inside the box. His reasoning was simple. The Path for the Mike linebacker is much easier then filling underneath a boxed fullback.

I like this concept, because it has your Middle linebacker run. He’s got a good angle on any tailback on the hole. The tailback’s shoulders won’t be able to square up on him either, and if the Sam get’s washed your Mike linebacker can still make the play.

It also works well if you run something in the quarters coverage family because your safety and potentially corner (in cover 2) will be there to help you on the spill.

4-3 over vs weakside iso

Your Sam linebacker doesn’t need to be a supreme athlete to do this. He just has to be athletic with good body control.

4-3 Over Front versus Slot Formation Weakside Iso

If you get slot formations with weakside iso, you can do a lot of different thinks depending on the scenario. If it’s in a scenario where you’re defending the pass more with the Sam apexed or wider versus to the slot side, the Mike would widen to his normal spot (outside shade of the guard, 4-5 yards deep). He would use a LEVER technique.

4-3 over vs weakside iso twins

Note the 3 Tech Spiking to A for cutback reasons. Can Apex Sam and play 2 Read (see my e-book) and spill to Sam/FS instead too.

In this case, the lever technique means he’s going to lever the runningback to his inside linebacker (the Will in this case). If they ran Iso to the Will or 3 technique side, we’d LEVER so the tailback goes to the Mike. In both cases, with tight action the opposite way, the inside linebacker who is not levering should scrape and fill underneath the other linebacker. The safeties are responsible for weakside cutbacks.

If you’re terribly worried about a good cutback back who keeps it north and south and don’t believe your defensive line can win over and over again to buy your secondary time, stunt the defensive tackles to help the secondary on the cutbacks. They would have to go less horizontal.

You can also change up the coverage and have the Sam play closer to the box. However, a benefit here is now the Mike linebacker is using a skill he’d use in the Under front too (Lever to the Will), which means a faster defense.

An Overview of the Spill, Box and Lever Rules

With that being said, here’s the basic spill and lever rules as I know some of you will want that. But first, let’s explain the roles.


The Mike and Will are considered the Inside linebackers. The Rover and Sam are Nickels, Outside Linebackers, or Inverts, however you want to group them. But this kind of gives you the traditional body type and athletic requirements we’re looking for at each position.

Spill and Box

The Sam and Rover, or Nickels, are SPILL players in the box, and when they’re outside the box they are BOX players (they box the play back inside to the help). A general rule of thumb is to Box if they’re outside the Box.

Lever, Spill and Box

The Mike and Will are almost always LEVER players. If they are ever outside the formation for some silly reason (this should hardly happen unless we get empty) they are then Spill or Box players, depending on where there help is. A general rule of thumb is to Box if they’re outside the Box, because that’s where help is usually coming.

Like I said though, it depends on numbers. when you get exotic formations, keep your answers simple.

Conclusions on the 4-3 Over Front versus Weakside Iso

Overall, the way the defense is built in this regard gives you the ideal matchups you want. Your Will linebacker, who in the under is free to roam, still has that ability. Your Sam linebacker, regardless of the role you pick for that player, is tough with good body control and can take on fullbacks.

The best part is you recycle run fits and technique. Not much is learned over again. Your best players can run and tackle, and ultimately that’s the name of the game. Occasionally they may hit a decent run, but this defense, because it’s so easy to play fast, will let your best players simply use fundamentals. This will ultimately limit explosive plays, and therefore points on the board.