Playbooks
The Under set in the 4-2-5 shifts the defensive line toward the offense's weak side. The NT shades the center to the strong side, the RDT slides into a weak side 3-technique, and the ends pinch to create one-on-one rushes against the guards and tackles. Standard 4-2-5 Even looks balance the line across the ball. Under instead overloads the interior rush lanes and walks the Sam-type defender down to the strong side edge, which gives you a run fit that looks like a 4-3 Under while keeping five defensive backs on the field. In the Big Nickel package that fifth DB is a third safety rather than a slot corner, so you get box physicality without giving up coverage speed against 11 and 12 personnel.
The tags tell you where the playbook's pressure comes from. The SUBLB fills the sub linebacker role and drives the second level run fits. The RLE and RRE crash angles set the edge, and the SLCB is the slot defender that Boundary CB Blitz and the man pressure calls isolate. Because the front is already shaded, the Under set disguises five and six man pressures well. Will Go Fire 3, Free Fire, Hammer 0 Blast and Cover 1 FS Fire all come from a pre-snap picture that looks identical to Cover 3 Match or Cover 4 Quarters.
Against offenses, Under is built to stop inside zone, duo and RPO glance concepts, where the offense reads a conflict defender. The third safety lets you match tight ends in man without a linebacker speed mismatch. The shell variety (Tampa 2, Cover 2 Invert, Cover 3 Sky WK, Cover 1 Hole) lets you rotate late and punish quarterbacks who read the safety alignment pre-snap. It is one of the most complete sub package sets for players who want run integrity and pressure disguise on the same snap.
Use Cover 3 Match and Cover 4 Quarters as your base on first and 10 against 11 and 12 personnel. User the SUBLB in the hook zone to take away the quick in breakers that attack the middle of the Under front.
On third and medium, show the Cover 2 Invert shell and then call Will Go Fire 3 or Free Fire from the same look. Quarterbacks who read two high safeties will set protection for a four man rush and get caught by the fifth rusher.
Against RPO heavy offenses, call Mike Sam Crash Press or SS Sam Crash Press to have the edge defender squeeze the give read. Shade the underneath coverage inside pre-snap to take away the glance and slant pass option.
Save Hammer 0 Blast and Safety Blitz for short yardage and red zone snaps where the field shortens the deep threat. Hot route the SLCB to press to disrupt the quick timing throws that beat zero pressure.
If the offense motions a speed slot toward the SLCB, audible out of Boundary CB Blitz and Cover 1 Slant Crash into Cover 2 Man or Cover 1 Hole. Then use a safety shade toward the motion to bracket the mismatch.