NFL Front & Gap Fit Simulator

Defensive Run Fit & Gap Control Lab

Simulate how defensive fronts hold up against modern NFL run blocking. Test Gerald McCoy's "Three W's" — Win upfront, Whack pullers, and Wrap & Flow — against inside zone, power, and counter concepts.

Scheme & Front Architect

Configure offensive concept and defensive alignment.

Matchup Presets

Offense (O) Orange

Run Blocking Concept Running Back Aiming Point

Defense (D) Blue

Defensive Front Alignment Defenders in Box

Light Box (6) 7 Defenders Heavy Box (8)

Extra defenders drop safety into alley to support C/D gap force.

The Three W's Run Stop Rules Coaching Lever

W1: Win Upfront (D-Line Technique) 2-Gapping clogs multiple lanes; 1-gap penetration risks cutback creases. W2: Whack the Puller / Edge Fit Spilling requires fast scraping LBs; boxing pins ball for interior pile. W3: Wrap & Flow (Linebacker Discipline) Over-pursuing creates gaping back-side holes against zone & counters.

Tactical Field & Collision Board

Ready to snap. Select alignment or press Snap Ball.

Play Outcome STUFF

Yards Gained 1.2 Yds

Defensive EPA +0.38

Run Success No

Vikings 3-4 Okie vs Bears Power-O

Point of Attack: Strong B-Gap

Scrub Time 0.00s

Coaching Film Room & Three W's Diagnostic Defense Won The Down

1. Win the Point of Attack

Nose tackle stalemates the center and controls both A-gaps. Guard cannot climb cleanly to the Mike linebacker.

2. Whack the Puller / Set Edge

Edge defender spills the pulling guard, absorbing the collision and forcing the running back into the scraping linebacker.

3. Wrap Up & Flow

Linebacker reads the puller, stays square in cutback lane, and closes downhill for a tackle at the line of scrimmage.

Gerald McCoy's "Three W's" Breakdown

As 6-time Pro Bowl defensive tackle Gerald McCoy detailed on NFL Network, stopping explosive NFL rushing attacks like Chicago's downhill ground game requires mastery of three non-negotiables:

Win upfront: Defensive tackles must reset the line of scrimmage, knock offensive linemen back a yard on the snap, and establish interior gap control before combinations can climb.
Whack pullers: On Power and Counter plays, the edge defender must strike pulling guards with inside leverage ("spill") or turn them inside ("box"), eliminating comfortable running lanes.
Wrap & flow: Second-level linebackers must mirror running back momentum without overrunning cutback angles, securing tackles on initial contact.

1-Gap vs 2-Gap Fronts in Today's NFL

Modern defensive coordinators like Minnesota's Brian Flores balance gap-cancellation front philosophies based on the opponent's run tendencies:

1-Gap Penetration: Defenders attack a designated shoulder crease. Generates negative plays (Tackles for Loss) but creates vulnerability to cutbacks if offensive linemen seal the angle.
2-Gap Stacking: Linemen strike the chest of the blocker, control the line of scrimmage, and shed to whichever gap the running back declares. Essential against heavy inside zone.
The "Bear" 5-2 Front: Places 3 interior defenders head-up on the Center and both Guards (0-tech and two 3-techs), eliminating immediate interior A/B gap running creases.

How Box Counts Dictate Run Mathematics

In 11-personnel matchups, the offense fields 5 linemen, 1 tight end, and 1 running back (7 primary blockers/runners). The run fit mathematics govern whether the run can succeed:

Light Box (6 Defenders): Offense has a +1 blocker advantage. The back has an unblocked path unless an interior lineman wins a 2-gap block upfront.
Neutral Box (7 Defenders): One-to-one gap parity. The game comes down to pad level, leverage, and tackling in the hole.
Heavy Box (8 Defenders): Defense walks down a Strong Safety into the box, giving the defense the unblocked free hitter in the alley.