Shift Duo

Check safety depth before the shift and again after it, if both safeties stay deep in a two high shell the box is lighter and Duo blocking should win at the point of attack. Watch the Mike linebacker's reaction to the shift motion, aggressive linebackers who crash downhill immediately can be sealed by the double team while disciplined linebackers who hold their gap will require a cutback read. This play struggles against stacked eight man fronts or heavy blitz packages that bring extra defenders into the box before the shift resolves, since the double team cannot account for an extra unblocked defender. Look for user-controlled defenders flowing hard to the shift side, an overzealous user linebacker or safety crashing down opens up a cutback lane away from the shift. Man coverage shells with no run support rotation are especially vulnerable since Duo blocking wins with double team push, while zone shells that stay disciplined and keep a linebacker in the alley can limit this play to short gains.