There are two basic ways to structure a defense: 1) Man-to-Man and 2) Zone. The true difference between these defenses is Coverage, or how they protect against the pass. In Man-to-Man, as the name suggests, the pass defenders are assigned to specific players. But in Zone Coverage, the pass defenders cover a specific area or zone on the field.
In Zone Coverage the type of scheme can be further broken down based on Deep Coverage, or how they protect against the pass in the deep zone (the part of the field closest to the defense’s own End Zone). Each Zone Coverage is named based on how many players are in Deep Coverage. In Cover 2 there are two players assigned to cover the deep zone (Free Safety and Strong Safety). In Cover 3, there are three players assigned to cover it (Free Safety and both Cornerbacks). Because of their deep position, initially these players are the only ones completely dedicated to Coverage and will not have run defense assignments (this is only initially because as the play unfolds, players may acquire new duties).
The players used for Deep Coverage will typically be any combination of the four Defensive Backs (Free Safety, Strong Safety and two Cornerbacks). The Defensive Backs not being used in Deep Coverage move up and usually cover the outer edges of the field, which include the Flat and the Curl zones.
Flat: There are two Flat zones and they are on the defensive side of the field. The Flat is the area within about 7 to 10 yards of the Line of Scrimmage and found along either sideline extending across the field to the Hash Marks (approximately 20 yards towards the middle of the field). The Flat is right underneath the Curl Zone.
Curl Zone: There are two Curl zones and they are on the defensive side of the field. The Curl is the area beginning about 7 to 10 yards downfield or past the Line of Scrimmage and found along either sideline extending across the field to the Hash Marks (approximately 20 yards towards the middle of the field). The Curl is right above the Flat and to the outside of the Hook (on either side of the Hash Marks).
Hook Zone: There are two Hook Zones and they are on the defensive side of the field. The Hook is the area beginning about 7 to 10 yards downfield or past the Line of Scrimmage and found directly across from where the Offensive Tackles are standing on the other side of the ball and extending towards the center/middle of the field. The Hook is directly next to and on the inside of the Curl.
| Deep ½ (FS) | Deep ½ (SS) | ||||
| Curl(CB) | Hook(LB) | Middle(LB) | Hook(LB) | Curl(CB) | |
| Flat | No Cover Zone (man-to-man)(DE) (DT) (DT) (DE) | Flat | |||
| ——line of scrimmage—– | |||||
