Duo

Identify the box count before the snap: a light box with four or five defenders is the green light to run Duo confidently. Watch the playside defensive tackle and linebacker alignment, since Duo is built to combo block a shaded nose or three technique before releasing to the linebacker, so a defense with a heavy shade or stacked linebacker directly over that gap can disrupt the double team timing. Key the mike linebacker's first step after the snap, if he flows hard downhill into the initial gap the ball carrier should bounce to the cutback lane created by the backside double team climbing late. This run struggles against gap exchange or scrape exchange defenses where the defensive end crashes down and a linebacker replaces him on the edge, so recognize odd front stacks or 46 style looks pre-snap as a warning sign. Zone blitzes and interior stunts that cross the double team assignments can blow up Duo before it develops, so if the defense shows a stunt or twist look at the snap, expect penetration and be ready to cut it back immediately.