Playbooks
Curl Flat out of Shotgun Stack HB WK is a classic zone beater built on the curl-flat combo to one side, paired with a curl or dig breaking underneath from the stack to create a natural high-low read on the flat defender. The HB releases to the flat as a checkdown option while the TE or stacked receiver works the curl at 10-12 yards, giving you a full progression from flat to curl to backside breaking route. This concept punishes Cover 2 and Cover 3 by stretching the underneath zone defenders horizontally and vertically, forcing a defender to choose between the flat and the curl sitting behind him.
Read the flat defender first, since Cover 2 corners sinking outside will open a throwing lane to the curl route running behind them. Watch the underneath linebacker responsible for the curl zone, because if he widens to the flat you have a clean window to the curl sitting down at the sticks. Against Cover 3, key the curl to flat side hook defender, if he shows zone drop depth late you can rifle the ball into the curl before he settles. Beware user controlled defenders lurking the flat or curl zones, since a jumped throw here gets picked off quickly by a spying linebacker or safety in a shallow drop. Man coverage looks (Cover 1 or Cover 0) with linebackers matched on the HB will limit the flat option, so shift your priority to the curl route working away from man leverage.
Pre-snap, identify if the corner is playing off or showing hard outside leverage, since that tells you whether the flat or curl will be open first against zone drops.
Use this on second and medium to second and long when you want a high percentage completion but still need to test a zone shell before committing to a shot play later in the drive.
Hot route the backside receiver into a drag or spot route if you diagnose Cover 3 pre-snap, giving yourself a fast underneath answer against a three deep shell.
Pair Curl Flat with Curl Switch in your play-calling sequence so the defense sees similar route distribution but has to respect a different leverage answer on the switch release.
Mix in RPO Zone Alert Screen or HB Slip Screen from the same set to keep linebackers from sitting hard on the curl flat combo once they start keying underneath routes.