A post pass pattern in football is a pass route in which the receiver runs downfield, then turns and runs towards the goal post in the endzone. The cut in the route is usually made between 10 and 12 yards downfield. The post is considered a long route, but is similar to the short slant route.
Posts are a key in the arsenal of a deep passing offense. The central idea is to use a post pass to expose a single high safety, especially those in cover 1 defense or cover 3. Putting two deep routes in the center of the field forces the high safety to choose who to defend, or assist with defending in the case of cover, which can lead to an open receiver or an uneven matching. Post routes can also prove effective in running off safeties and corner to open up the short run game.
There is also a variant of the post where the cut is made at a shallower angle, and this is referred to as a skinny post. Skinny posts are designed to expose the gaps between deep defenders. The idea is to run the route between the gaps of a sideline defender's zone and the close safety's zone. This creates confusion in whose responsibility it is cover the skinny post, typically leading to the skinny post being uncovered or double covered. In the event the skinny post is double covered, another route is typically open.
The most effective strategy for stopping post routes is the same for any long pass route: an effective pass rush game. Because posts are slow-developing, deep routes, pressuring the quarterback will reduce effectiveness of the long game. Regardless of whether the secondary is in man or zone, whether the receiver is covered or not, a good pass rush will stop a long pass play before the routes can even develop.
In the secondary however, covering post routes relies on a safety whose head is on the swivel. The man in middle field coverage has to be ready to take over for defending the post route seamlessly as he crosses from a sideline quarter or third to the middle quarter or third. This is all contingent on the defense running a cover 3 or cover 4 defense. In the event the receiver runs a skinny post and hits the area between the quarters or thirds, the corner and safety must communicate to decide who covers the skinny post, and who covers another route. That distinction most often lies in who has another receiver in their zone.
In the event of a post against man defense, the only real strategy is taking away the outside shoulder and not allowing the receiver to get deeper than the defender. This means that the defender needs to be faster than the receiver and able to react to the cuts while still allowing little separation.