During the course of an American football game, a team’s offense often finds that one pass play works particularly well against a certain defense and matchup. To keep using the play in that game and to continue to confuse the defense, the offense often disguises that play by running it out of different formations while maintaining similar pass routes.
As an example, here’s a successful offensive play. Three receivers (WR), a tight end (TE), and a running back (RB) line up:
One receiver is to the left.
The running back is also behind the line to the left, behind the left tackle.
The tight end is aligned to the right.
Two other receivers are outside of the tight end.
Then, they execute the play:
The receiver on the left runs down the field 18 yards and runs a square-in.
The tight end runs a crossing route, about 7 or 8 yards from the line of scrimmage.
The running back swings out of the backfield to the left.
The receiver located in the slot to the right simply runs right down the middle of the field. He’s the deep decoy receiver who’s going to pull all the defensive players out of the middle.
The quarterback wants to hit the receiver who lined up on the left side. If he isn’t open, he tries the middle with the tight end; lastly, he dumps the ball to the running back.
To modify this successful play, the offense makes a few changes:
The same receiver on the left runs the same 18-yard square-in.
The running back on the left releases to that side, but this time he runs across the line of scrimmage 7 or 8 yards and curls back toward the quarterback. The back is now assuming the role of the tight end in the original formation.
The tight end runs down the middle of the field.
The receiver in the slot runs right between the two hashes and hooks.
So, it’s pretty much the same play. The offense’s target remains the receiver to the left. And all those other receivers are simply decoys.