Playbooks

HB Mtn Dig Spot runs out of Shotgun Bunch Str Offset with a pre-snap HB motion across the formation that flips the strength and gives you a clean coverage indicator before the snap. Post-snap, the outside receiver runs a deep vertical clear-out on the right while the inside bunch receiver breaks off a quick out to the sideline underneath it, and the backside receiver runs a long developing dig across the middle of the field, with the motion man releasing to the opposite flat as a checkdown and pressure valve. This is a Cover 3 beater built on the spot concept, using the flat-out combo to hold underneath defenders while the dig sits down in the vacated middle zone, so the primary read progression is dig first if the linebackers widen with the flat route, then the vertical clear-out on a bust, and the HB flat as the safety valve against pressure.
Watch the flat defender and outside cornerback pre-snap, if they are sitting shallow and the safety is rolled to one side you are likely seeing Cover 3 and the dig window will be open. Post-snap, key any user-controlled defender sitting in the middle of the field (lurk technique), since that is exactly the spot this dig route is designed to attack and a smart user can jump the throw. If linebackers show blitz and vacate the middle hook zone immediately at the snap, expect man coverage behind it, which favors the dig against a trailing defender but exposes the HB flat route to a free rusher. Cover 2 and Cover 4 shells with two deep safeties can squeeze the dig route since there is more help over the top, so be ready to check down to the HB flat or the underneath out route instead of forcing it deep. Disguised zone blitzes that show press man pre-snap but drop into zone post-snap are the biggest threat to this concept, so track second-level defenders after the snap rather than trusting the pre-snap picture alone.
Use the HB motion pre-snap to bait linebackers into revealing man or zone, if they run with the HB it is man coverage and the dig has a favorable path against a chasing defender.
Against Cover 3 or Cover 4 shells, key on the flat defender since holding him with the spot route opens the dig window over the middle for an easy in-between-the-hashes throw.
This play works best on second and medium to second and long when you need a chunk gain, since the dig route develops a bit late and needs room to work.
If the defense shows heavy underneath zone or a nano blitz look, hot route the dig into a quicker option or check it down to the HB flat immediately rather than forcing the window.
Pair this with Verts Dig or Mtn Deep Post from the same set to keep defenses honest on the vertical shot, then come back to HB Mtn Dig Spot once safeties start cheating up to stop the shorter game.