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The 4-3 Under: How the Chiefs’ current personnel fits

How does a switch change the outlook for the Chiefs current personnel?

New York Giants v San Francisco 49ers Photo by Ezra Shaw/Getty Images

With the hiring of new defensive coordinator Steve Spagnuolo, the Chiefs are likely seeing a switch from their 3-4 defense to the 4-3. That’s caused a lot of consternation amongst Chiefs fans, but where are the biggest problems for the Chiefs in this switch?

I’m going to give you a quick-and-dirty look at where some players can fit, position responsibilities and who are the winners and losers of the formation switch.

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The 4-3 variant that Spagnuolo chooses to use is similar to that utilized by his mentor and former Andy Reid defensive coordinator Jim Johnson, called the 4-3 Under. The 4-3 Under front shares quite a few similarities to that of the Chiefs 3-4 defense, making this transition easier.

Weak-side defensive end - The Weak-side defensive end — also called the “LEO” — in the 4-3 Under is typically the best pass rusher on the team. Putting his hand in the dirt, this defender is responsible for weak-side run contain opposite the tight end and getting after the quarterback. With the Chiefs current personnel, this would be an easy fill for Dee Ford. Limited coverage responsibility, ability to set an edge, and — most importantly — a great pass rusher are all things that we’ve seen from Dee Ford this season.

3 Technique - Lining up to the same side as the weak-side defensive end, the 3-tech is a penetrating player capable of beating a guard one on one. This position is typically a player that has a solid get-off, can knife to either side and has the speed to attack the run from the back side. Once again, an easy fit — and potentially a better fit in the 3-4 base defense — for Chris Jones. Jones can utilize his speed and strength to collapse on the run, get after the passer, and find plenty of great matchups one on one in a 4-3 under front.

1 Technique - Opposite of the 3 technique, the 1 technique is typically a 2-gap player, getting doubles against the strong-side guard and center, freeing up the linebackers behind him to make stops. This is usually filled by a player in an “under tackle” or “nose guard” mold, which the Chiefs have in Derrick Nnadi and Xavier Williams. Both will have to command a double team to keep the linebackers clean, and both should be plenty capable.

Strong-side defensive end - Lined up to the strong side of the offense, this defensive end will be between the tight end and the tackle, and their primary responsibility is as a run stuffer with a minimal amount of pass rush ability. This is actually a perfect fit to try to maximize last year’s second-round pick Breeland Speaks. Speaks is solid against the run, but looks uncomfortable in space, something he won’t have to contend with often lined up in this spot. With some wanting to kick Speaks inside to 5-tech in the Chiefs 3-4 defense, this situation presents a better opportunity for Speaks to develop as a starting player for the Chiefs.

SAM linebacker - When most think of the 4-3 defense, they think of three off-ball linebackers on the second level behind four defensive linemen. With the 4-3 Under, one of those off-ball linebackers shifts down close to the line of scrimmage — still standing — and can rush the passer or drop into coverage to carry a tight end to the safeties in the second level. During Spagnuolo’s second run as a defensive coordinator with the New York Giants, he acquired Olivier Vernon and Devon Kennard. Vernon played this role sparingly, but was still effective. Vernon is a large outside linebacker with limited coverage ability but was able to defend the run very well off of the tight end and could find a lot of success as a pass rusher standing up. If that sounds familiar to you, it should — it’s quite similar to what Justin Houston has offered the Chiefs recently.

*However, Kennard was the primary option for Spagnuolo in his second run. A 256-pound linebacker with good rush skills, Kennard offered a little more speed as a hybrid player off the edge, able to carry a tight end to the safety.

Depending on if Spagnuolo goes bigger or smaller, Houston could be a fit in this role should the Chiefs retain him.

Mike linebacker - Shading between the 1-tech and the 3-tech at the second level, the Mike linebacker’s responsibility in the 4-3 under are to cover a short hook zone in the center of the field and to attack the run. With his limited coverage ability shown this season — as well as a much more familiar four-man front in front of him, like he saw in Dallas — Anthony Hitchens is a solid fit in this role. He’ll be less exposed in coverage, can set the fronts, and attack downhill more readily instead of being asked to cover multiple gaps as the weak-side linebacker in the Chiefs 3-4.

Will linebacker - Sitting behind the weak-side defensive end and the 3-tech, the will linebacker is tasked with keying off of the running back in the run game and kicking out into man coverage or the flats against the pass. This will linebacker is typically kept clean by the defensive linemen in front of him, allowing him to attack as unimpeded to the running back as he can from the weak side of the formation. As a good coverage linebacker and a guy that struggles to stack and shed blockers, Dorian O’Daniel might gain the biggest advantage in a scheme switch. The Chiefs could find themselves in a great position to utilize last year’s third-round pick.

When the Chiefs change to their sub package — something that every NFL team runs as their primary package — this evolves easily. The Chiefs can remove the 1-tech, shift the strong-side defensive end inside, and bring the SAM down — a 4-2 front similar to that they’ve used in the past — or they can remove the strong-side defensive end and stay big in the middle to protect against the run, still as a 4-2 front.


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Breeland Speaks is a big winner here, having a true position on the field. His ability to kick inside in the sub package and play the run in the base are hugely beneficial for the Chiefs. Dorian O’Daniel and Anthony Hitchens would be in significantly more comfortable roles for the style of play they are capable of, and that should only improve the Chiefs run defense and coverage ability. Chris Jones is also a big winner, seeing more one-on-ones in the base defense and he too could find snaps in Speaks’ strong-side defensive end role if the Chiefs wanted to develop a more penetrating front on some plays.


NFL: AFC Championship Game-New England Patriots at Kansas City Chiefs Denny Medley-USA TODAY Sports

Reggie Ragland simply doesn’t have a home in a 4-3 Under. He isn’t strong enough to set an edge or rush the passer to play the way Spagnuolo utilizes his SAM, and he’s not a better option at the Mike than Anthony Hitchens. Tanoh Kpassagnon is also not a great option at SAM due to his run defense, and not a good enough pass rusher as a LEO to come off the other EDGE.

With the Chiefs having to make some serious decisions at pass rusher — Justin Houston’s bloated contract and Dee Ford’s impending free agency — they’ll have to decide if they need to keep both, or which position they’ll have to fill this offseason. While the LEO position is arguably the most important in the front, the skillset of the SAM is a difficult one to find.

So there’s where the current personnel would fit into a Spagnuolo 4-3 Under base defense. Do you feel better about the switch? Worse?

Where do you think the Chiefs need to attack to improve it in free agency and in the draft?

*Writer’s note: After watching more games, the SAM Linebacker player profile for Spagnuolo needed to be updated to reflect the usage more accurately. Originally, Vernon got looks as the primary defender in the games I watched.

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