4-3 Under
Weak-side shade, SAM on the edge
- Front
- Linebacker
The 4-3 Under shifts the defensive line toward the weak side, moving the 3-technique to the weak B-gap and walking the SAM linebacker up to the line of scrimmage as a de facto defensive end. This front is built for the Tampa 2 coverage shell, creating a 5-man surface with strong-side edge pressure from the SAM. The under shift naturally creates a difficult run fit for offenses trying to run toward the strong side.
Assignments
7 PLAYERSNumbers match the keys on the field. Tap a player for his gap rules.
Strengths4
- Strength: Ideal for the Tampa 2 coverage, giving the MIKE a clean drop to the deep middle
- Strength: SAM as a walked-up edge rusher creates a 5-man pass rush surface
- Strength: Under shift hardens the strong-side surface (3-tech weak + 4i/5 + SAM on the edge) and makes tight-end-side runs difficult
- Strength: Strong-side run fits are reinforced by the SAM and DE working together
Weaknesses3
- Weakness: Strong-side B-gap can be soft if the MIKE is slow to fill
- Weakness: SAM must be a true edge rusher, limiting personnel flexibility
- Weakness: Vulnerable to strong-side power if the NT gets moved off the ball
Pairs well with
3History
The under-shifted 4-3 traces back to Jimmy Johnson's Miami Hurricanes in the mid-1980s, with Buddy Ryan running under-shifted concepts even earlier. Monte Kiffin paired the front with Tampa 2 coverage at the Buccaneers in the late 1990s, popularizing it as the foundation of an era-defining defense, Warren Sapp at 3-technique became the prototype for the under-shifted interior disruptor. Pete Carroll later refined the strong DE into a 4i to better defend modern outside-zone schemes.
Run game vs the 4-3 Under
9 RATED- Inside ZoneEdge
Double-teams on the nose and 3-technique create movement at the point of attack; MIKE is slow to fill against zone tempo.Show reasoning
Conflict defender. MIKE linebacker (A-gap)
Why the offense wins. Double-teams on the nose and 3-technique create movement at the point of attack; MIKE is slow to fill against zone tempo.
Key adjustment. Fire the MIKE into the A-gap pre-snap and have the 3-technique two-gap to clog the lane.
- PowerEdge
Running at the under front's weak side, the tackle has a down angle on the 3-technique, the FB kicks out the 5-tech end and the backside guard wraps for the WILL; the strong-side overload is away from the ball.Show reasoning
Conflict defender. Weak-side defensive end (kick-out target)
Why the offense wins. Running at the under front's weak side, the tackle has a down angle on the 3-technique, the FB kicks out the 5-tech end and the backside guard wraps for the WILL; the strong-side overload is away from the ball.
Key adjustment. Have the 5-tech wrong-arm the kick-out to spill the ball to the scraping WILL.
- CounterEdge
Misdirection holds the backside DE while the guard kicks out the playside end; the pulling tackle leads through the hole.Show reasoning
Conflict defender. Playside defensive end (kick-out target)
Why the offense wins. Misdirection holds the backside DE while the guard kicks out the playside end; the pulling tackle leads through the hole.
Key adjustment. Have the playside end wrong-arm the kick-out and the backside end chase flat down the line.
- DuoEdge
Duo double-teams blow the DTs off the line; the WILL cannot scrape fast enough to fill the cutback.Show reasoning
Conflict defender. WILL linebacker (cutback lane)
Why the offense wins. Duo double-teams blow the DTs off the line; the WILL cannot scrape fast enough to fill the cutback.
Key adjustment. Slant the DTs away from the double-teams to disrupt the blocking angles.
- TrapEdge
The under front's weak-side 3-technique is the premier upfield penetrator in football — exactly the lineman trap is built to kick: he rushes the B-gap, the backside guard kicks him out, and the ball hits inside his vacated charge.Show reasoning
Conflict defender. Weak-side 3-technique (trap target)
Why the offense wins. The under front's weak-side 3-technique is the premier upfield penetrator in football — exactly the lineman trap is built to kick: he rushes the B-gap, the backside guard kicks him out, and the ball hits inside his vacated charge.
Why the defense wins. The under front alignment makes the trap angle more difficult for the pulling guard.
Key adjustment. The 3-tech must read the guard's down block and squeeze flat down the line instead of penetrating.
- Outside ZoneToss-up
The 5-technique sets the edge against the reach and the WILL scrapes over the top, so the stretch has to bend back into the 3-technique and the MIKE.Show reasoning
Conflict defender. Weak-side defensive end (5-technique, reach block)
Why the offense wins. Run it weak: the 3-technique and 5-technique give clean reach angles away from the SAM, and the back's bang-bend read punishes the under front's strong-side overload.
Why the defense wins. The 5-technique sets the edge against the reach and the WILL scrapes over the top, so the stretch has to bend back into the 3-technique and the MIKE.
Key adjustment. Have the 5-tech hold the edge against the reach and the WILL scrape over the top.
- Zone ReadToss-up
The SAM is already wide and on the line, so he can sit on the keep while the 4i end and the MIKE take the give; the scrape exchange is built into the front.Show reasoning
Conflict defender. Walked-up SAM (9-technique read key)
Why the offense wins. The read is the walked-up SAM at the 9-technique; if he squeezes the give, the QB pulls and gets outside him while the 4i end is blocked down inside.
Why the defense wins. The SAM is already wide and on the line, so he can sit on the keep while the 4i end and the MIKE take the give; the scrape exchange is built into the front.
Key adjustment. Have the SAM sit on the QB and let the 4i end and MIKE take the give.
- Toss/SweepTough
Running the toss weak into the under front, the 5-technique end is on the edge with the WILL stacked behind him and the 3-tech squeezing from inside; the sweep is strung out.Show reasoning
Conflict defender. Weak-side defensive end (5-technique edge)
Why the defense wins. Running the toss weak into the under front, the 5-technique end is on the edge with the WILL stacked behind him and the 3-tech squeezing from inside; the sweep is strung out.
Key adjustment. Have the 5-tech squeeze the edge and the WILL run the toss down from inside out.
- Jet SweepTough
Running the jet to the under front's weak side, the 5-technique end is already on the edge with the WILL stacked behind him, so the sweep is forced back into pursuit.Show reasoning
Conflict defender. Weak-side defensive end (5-technique edge force)
Why the defense wins. Running the jet to the under front's weak side, the 5-technique end is already on the edge with the WILL stacked behind him, so the sweep is forced back into pursuit.
Key adjustment. Have the 5-tech squeeze the edge and the WILL run the sweep down from inside out.