Defenses count to "four mississippi" before crossing the line of scrimmage - unless:
- The ball has left the quarterback's hands via a pass, handoff, kick, or dropped ball.
- There is any downfield blocking by an offensive player. Downfield blocking by the offense allows the defense to cross the line of scrimmage at will.
- There is a fumble in the backfield or the snap has been muffed (i.e. the ball hits the ground or is dropped by the quarterback during the hike.)
- The defense calls a blitz.
In any of these instances the defense can cross the line of scrimmage immediately.
Note: "Crossing the Line of Scimmage" means any part of the body going over the line. Therefore reaching over the line to tag the QB before the "4 Mississippi" count is not allowed.
Defenses do not have to rush the quarterback (they may choose to double-team a receiver instead), however they must audibly count to "4 Mississippi" anyway so everyone on the field knows what's going on.
The "4 Mississippi" count can be quick but it must be audible across the whole field.
Intentional grabbing/pulling of clothing is not allowed under any circumstances, even for defensive linemen trying to shed a block. Grabbing is a 15 pace penalty from the spot of the infraction.
Defenders may not line up directly over the center.
Last updated: Sep.15.2017