Today, I'm going to break down two basic principles of the Virginia Tech offense and defense matched against each other—the zone stretch versus the gap fit.
In Bud Foster's gap defense, each of the front-six defenders (all four down linemen and the two inside linebackers) have responsibility to attack a gap and either make a play in the gap or occupy it without being driven out. The outside "linebacker-safeties" (Whip and Rover) are edge players. Based on a defensive call they either "force" the play, playing outside contain to force the running back to the inside, or "spill" the play, attacking the inside shoulder of the running back, forcing him to bounce outside to an unblocked alley player which is often the free safety. Against teams that zone block running plays, the normal "key" for an interior player is go where the offensive lineman goes, cross his face, and fit the gap to his outside.