Seattle Cover 3 defense

[4][5][n 1] Unlike the standard 4–3 under, in which all the defensive linemen employ one gap techniques, the Seattle variant has a split personality.

The combination of two 2 gap defensive linemen and "8 in the box" means the formation is powerful against the run.

[13] This was also about the time Dan Quinn convinced Red Bryant to play the big end position, to make use of his ability to two gap[14][15][16] The resulting hybrid front became successful.

[17] In part, it was successful by finding functional use of players like Kam Chancellor, who would have been regarded as a positionless "tweener" by more traditional NFL defenses.

[18][19] By 2013, this scheme helped lead the Seattle Seahawks to two Super Bowls, and was so effective the defensive secondary acquired its own nickname, the Legion of Boom.

The defensive using a 4-3 under reduced front. Yellow triangles are linemen, yellow squares are linebackers, yellow circles are defensive backs. The two linemen to the left of the offensive center use a 1 gap technique, while the two to the right of the offensive center use a 2 gap technique. Left to right the linemen's roles are the Leo, the 3 tech, the nose tackle, and the big end.