Playbooks

Y Shallow Cross out of Singleback Doubles Flex lines up two receivers to the left with the flexed TE tight to the formation and a lone receiver isolated to the right. At the snap the flexed TE runs the shallow crossing route underneath from left to right all the way across the formation, while the inline slot receiver breaks outside on a square out and the outside receiver stems vertically before turning it into a corner route up the sideline. The lone receiver to the right runs a straight vertical seam and the running back releases on a check release into the shallow area, giving the quarterback a levels concept with the shallow drag as the primary read against man coverage and the square out as the zone beater underneath if the crosser is taken away.
Pre-snap, check safety depth: a single high safety usually means man coverage underneath, which sets up the shallow crosser to beat man to man matchups easily. Watch the flexed TE at the snap, if a linebacker or nickel defender tries to trail him across the field in man coverage, that confirms man and the crosser will win most reps. In zone coverage, key the underneath linebackers' drop depth, if they sink too far the square out and shallow route both sit in soft spots for easy completions. Look for a user controlled defender lurking in the shallow zone or spying the crosser, that is the biggest threat to this concept and should push the quarterback to the corner route or vertical seam instead. If the defense blitzes off the edge and rushes five or six, the shallow route becomes a built in answer since it clears the box fast before the pressure arrives.
Use this on early downs or third and short since the shallow cross gives you a high percentage completion underneath against both man and zone.
Read the flexed TE's shallow crosser first, it is the primary man beater because it creates natural rub traffic that forces defenders to fight through trash.
If the defense shows a two high safety shell pre-snap, expect the corner route and vertical seam on the right to have room to work, so be ready to hot route the shallow route deeper if the underneath zone is clogged.
Pair this play with Slot Cross or Inside Cross earlier in a drive so the defense starts jumping the shallow route, then hit the corner route on the outside receiver for an explosive play once they overcommit.
Against aggressive man blitzes, get the ball out on the shallow route quickly since it clears the middle fast and protects against a nano blitz coming off the edge.