Playbooks
At a Glance
Overview
4-3 Under is a defensive set, not an offensive one, and that changes how you should think about every play listed here. Instead of the balanced, symmetrical fronts you get out of 4-3 Over or 4-3 Stack, Under shifts the strength of the line away from the tight end: the nose tackle slides to the weak side A gap, the strong side defensive tackle heads to the 3 technique, and the Sam linebacker walks up over the tight end while the Will and Mike stack behind the shifted front. The NT tag matters because it tells you the interior is built around a true nose, so you are asking a big body to eat single blocks and let the linebackers scrape clean rather than asking four gap penetrators to win one on one.
That alignment is why the run fits play so differently than a standard 4-3. Under gives you a hard edge to the tight end side with the Sam essentially playing a stand up end, so gap runs, stretch plays, and outside zone into the strength get walled off before the back can get vertical. The tradeoff is a lighter weak side, which is exactly why plays like Will Go Fire 3, Free Fire, Free Fire Ls, and Cover 1 FS Fire exist in this set: they send the weak side pressure that the front already threatens, so the offense has to declare protection before the snap.
The coverage menu here is unusually deep for a base front, which is what makes Under a legitimate every down set in competitive play. You get the full man rotation (Cover 1 Hole, Cover 1 Hole Press, Cover 1 Robber Press, Cover 1 Contain Press, Cover 2 Man), the full zone rotation (Cover 3 Match, Cover 3 Seam Press, Cover 3 Hard Flat, Cover 3 Sky WK, Cover 4 Quarters, Tampa 2, Cover 2 Invert, 2 Invert Hard Flat), and true pressure looks (Safety Blitz, Sam Blitz 2, WK Corner Blitz, Mike Sam Crash Press, SS Sam Crash Press, Hammer 0 Blast). Because the shell is disguised by the same front on every snap, you can run press man and quarters out of an identical pre snap picture and force the quarterback to guess whether the boundary receiver is isolated in man or bracketed.
Strengths
- Elite run defense to the tight end side: the shifted nose and Sam walked up over the TE close the strong side C and D gaps, so outside zone and power into the strength get spilled to unblocked help.
- Coverage disguise is the best feature here. Cover 1 Hole Press, Cover 3 Seam Press, and Cover 4 Quarters all show the same press alignment, so the offense cannot diagnose man versus zone before the snap.
- Cover 1 Hole and Cover 1 Robber Press give you a free rat defender in the middle of the field, which kills drags, shallow crossers, and mesh concepts that normally beat pure man.
- Built in weak side pressure with Free Fire, Will Go Fire 3, and Cover 1 FS Fire attacks the light side of the front while still keeping a three deep shell behind it.
- Tampa 2 and Cover 2 Invert cover the seam and deep middle without needing a blitz, which is the answer when an opponent lives on tight end verticals and post digs.
- Mike Sam Crash Press and SS Sam Crash Press let you crash the front and user the resulting free defender, giving you contain and a QB spy in the same call.
Weaknesses
- The weak side is undermanned by design. Counter, pin and pull, and outside zone away from the tight end will find a soft edge unless you shade the line or user the Will.
- Base 4-3 personnel means three linebackers on the field. Motion a slot to the perimeter and any of your linebackers gets isolated on a receiver in man coverage.
- Trips and bunch formations stress the Sam and the flat defenders in Cover 3 Hard Flat and 2 Invert Hard Flat, leaving the curl to flat window open for smart route combos.
- Only a four man rush on the base coverage calls. Elite quarterbacks with clean pockets will pick apart Cover 3 Match and Cover 4 Quarters if you cannot generate pressure with four.
- Hammer 0 Blast and Safety Blitz remove your deep help entirely. One missed press or one hot routed slot fade and you give up a touchdown instead of a sack.
- Under is a run first alignment, so the pass rush lanes are less clean than a 4-3 Over or Nickel front. Interior pressure through the A gap is slower to arrive.
Usage Tips
Use Under as your base run down defense against single tight end sets and 21 personnel. It is the correct answer to inside zone and power on first and second down.
Pair Cover 1 Hole Press with Cover 3 Seam Press in the same series. The pre snap picture is identical, so the quarterback has to hold the ball an extra beat to read the safety rotation.
User the free safety in Cover 1 Hole and Cover 1 Robber Press. Playing the robber yourself lets you sit on the dig and crossing routes that the AI rat defender is slow to trigger on.
Shade the line inside or pinch the ends when you expect a run away from the tight end. That fixes the weak side gap without giving up your coverage shell.
Save Hammer 0 Blast and WK Corner Blitz for third and long or obvious pass situations where you have already shown four man rush looks on the previous snaps.
Against trips and bunch, get out of Under and into a Nickel or Big Dime set. Three linebackers against three receivers is a matchup you do not want in man coverage.
Manually press your boundary corner and back the safety off in Cover 2 Man to build a soft bracket on the opponent's number one receiver.
