Playbooks

Z Spot Shake is a Cover 3 beater run out of Shotgun 5WR Tight (00 personnel) with no backfield help, so this is a pure dropback pass with no run or play-action element. Off the diagram, the two receivers to the left run vertical stretch routes (a deep corner route and an underneath out to the sideline) while the right side shows the spot concept: the inside slot runs a shake/spot route sitting underneath, the outside receiver next to him breaks flat, and the far right receiver runs a corner route stretching the deep third. The primary read progression works right to left: start with the shake/spot route sitting in the hole against Cover 3, work to the flat defender underneath, then check the deep corner route on the backside if the zone rotates away from the shake concept.
Pre-snap, check the depth of the safeties and if you see two-high shifting to one-high at the snap, expect Cover 3 and jump the shake route immediately since that is exactly what this play is designed to attack. Key the middle linebacker's drop, if he sinks hard into the shake route window, be ready to check down to the flat route underneath him. Watch for a user-controlled defender lurking in the shallow middle zone, since that is the exact area the shake route is designed to occupy and a smart user can sit on this route. Man coverage with no deep safety help is the biggest counter to this concept, since the shake route has no natural pick or rub to separate from a trailing defender. A hard blitz off the edge with no drop-eight zone behind it can also disrupt this play since there is zero backfield protection help against extra rushers.
Pre-snap, identify whether the defense is showing a 3-deep shell or a single high safety, since this concept is built specifically to exploit the hole in Cover 3 zones.
If the corner over the shake route is playing hard outside leverage, hot route the flat runner earlier or slide him deeper into the void to keep him away from the underneath linebacker.
Use this play on second and medium to third and short situations where defenses are more likely to sit in zone rather than blitz, since there is no protection help from the backfield.
Pair Z Spot Shake with Mesh or Mesh Post from the same set to attack man coverage on the next snap, forcing the defense to guess between zone and man beaters.
Against teams that disguise coverage post-snap, hold the ball one tick longer and let the shake route settle into open grass before pulling the trigger.