In American football, a two-level defense is a defensive formation with only two layers of defense instead of the customary three layers.
In a standard three-level defense, there are three layers: the forcing unit (consisting mainly of linemen but possibly also including blitzing linebackers and defensive backs), the underneath coverage (usually consisting of linebackers but possibly including other players, especially in the case of a zone blitz), and the contain unit (mostly defensive backs). A two-level defense does away with the contain unit in favor of increased pressure on the offense. Two-level defenses will often use one deep safety (as deep as 28 yards at the snap) to enforce an end line on the offense, but the Bear 4-6 is a two level defense with contain handled solely by the single coverage skills of the cornerbacks. The "Bear" can also function as a three-level defense, and indeed concealment of the defensive structure is a key to making this defense work.
The two-level was invented to combat the run and shoot offense in the 1980s, but has stayed in use due to its adaptability in combating all types of offenses. The defense of spread formations remains a strong suit of this model.
A cornerback (CB) is a member of the defensive backfield or secondary in gridiron football. Cornerbacks cover receivers most of the time, but also blitz and defend against such offensive running plays as sweeps and reverses. They create turnovers through hard tackles, interceptions, and deflecting forward passes.
A linebacker is a playing position in gridiron football. Linebackers are members of the defensive team, and line up approximately three to five yards behind the line of scrimmage and behind the defensive linemen. They represent the "middle ground" of defenders, playing closer to the line of scrimmage than do the defensive backs, but further back than do the defensive linemen. As such, linebackers play a hybrid role and are often the most versatile players on the defensive side of the ball; they can be asked to play roles similar to either a defensive lineman or a defensive back. How a linebacker plays their position depends greatly on the defensive alignment, the philosophy of the coaching staff, and the particular play the offense may call.
In gridiron football, blitzing is a tactic used by the defense to disrupt pass attempts by the offense. During a blitz, a higher than usual number of defensive players will rush the opposing quarterback, in an attempt either to tackle him or force him to hurry his pass attempt.
Strategy forms a major part of American football. Both teams plan many aspects of their plays (offense) and response to plays (defense), such as what formations they take, who they put on the field, and the roles and instructions each player are given. Throughout a game, each team adapts to the other's apparent strengths and weaknesses, trying various approaches to outmaneuver or overpower their opponent in order to win the game.
The 46 defense is an American football defensive formation, an eight men in the box defense, with six players along the line of scrimmage. There are two players at linebacker depth playing linebacker technique, and then three defensive backs. The 46 defense was originally developed and popularized with the Chicago Bears by their defensive coordinator Buddy Ryan, who later became head coach of the Philadelphia Eagles and Arizona Cardinals.
In American football, a zone blitz is a defensive tactic that sends additional players to rush the opposing team's quarterback, whilst also unexpectedly redirecting a supposed pass rushing player into pass coverage instead. This tactic also likely includes zone coverage.
The Tampa 2 is an American football defensive scheme popularized by the Tampa Bay Buccaneers National Football League (NFL) team in the mid-1990s–early 2000s. The Tampa 2 is typically employed out of a 4–3 defensive alignment, which consists of four linemen, three linebackers, two cornerbacks, and two safeties. The defense is similar to a Cover 2 defense, except the middle linebacker drops into a deep middle coverage for a Cover 3 when he reads a pass play.
In American football, the specific role that a player takes on the field is referred to as their "position." Under the modern rules of American football, both teams are allowed 11 players on the field at one time and have "unlimited free substitutions," meaning that they may change any number of players during any "dead ball" situation. This has resulted in the development of three task-specific "platoons" of players within any single team: the offense, the defense, and the so-called 'special teams'. Within these three separate "platoons", various positions exist depending on the jobs that the players are doing.
Safety, historically known as a safetyman, is a position in gridiron football which is played by a member of the defense. The safeties are defensive backs who line up from ten to fifteen yards from the line of scrimmage who can play as linebackers or deep as normal safeties. There are two variations of the position in a typical American formation: the free safety (FS) and the strong safety (SS). Their duties depend on the defensive scheme. The defensive responsibilities of the safety and cornerback usually involve pass coverage towards the middle and sidelines of the field, respectively. While American (11-player) formations generally use two safeties, Canadian (12-player) formations generally have one safety and two defensive halfbacks, a position not used in the American game. As professional and college football have become more focused on the passing game, safeties have become more involved in covering the eligible pass receivers.
There are several defensive formations commonly used in eight-man football. Defensive formations are classified by the total number of linemen and linebackers in the formation. The three basic types of formations in eight-man football are seven-man fronts, six-man fronts and five-man fronts.
The New England Patriots generally run a modified Erhardt-Perkins offensive system and a Fairbanks-Bullough 3–4 defensive system, though they have also used a 4–3 defense and increased their use of the nickel defense.
In American football, the 3–4 defense is a common defensive alignment consisting of three down linemen and four linebackers. It is a called a "base defense" because it is the default defensive alignment used on "base downs". However, defenses will readily switch to other defensive alignments as circumstances change. Alternatively, some defenses use a 4–3 defense.
Zone coverage is a defense scheme in gridiron football used to protect against the pass.
In American football, the 3–3–5 defense is a defensive alignment consisting of three down linemen, three linebackers, and five defensive backs. The 3–3–5 defense can also be referred to as the 3-3 stack and the Spread Defense. It is one form of the nickel defense, a generic term for a formation with five defensive backs. Veteran college football defensive coordinator Joe Lee Dunn is widely credited with being the main innovator of the 3-3-5 scheme.
The following terms are used in American football, both conventional and indoor. Some of these terms are also in use in Canadian football; for a list of terms unique to that code, see Glossary of Canadian football.
In American football, the 4–4 defense is a defensive alignment consisting of four down linemen and four linebackers.
In American football, the dime defense is a defensive alignment that uses six defensive backs. It is usually employed in obvious passing situations. The formation usually consists of six defensive backs, usually two safeties, and four cornerbacks, and has either four down linemen and one linebacker, or three down linemen and two linebackers. This formation is used to prevent the offense from completing a medium- to long-range pass play. This may be because the offense's running game is inefficient, time is an issue, or they need a long pass for a first down. It is also used against teams whose pass-to-run ratio predominantly favors pass. The formation, however, is vulnerable to running plays as the formation is missing two linebackers, or a linebacker and a down lineman.
The run and shoot offense is an offensive system for American football which emphasizes receiver motion and on-the-fly adjustments of receivers' routes in response to different defenses. It was conceived by former high school coach Glenn "Tiger" Ellison and refined and popularized by former Portland State offensive coordinator Mouse Davis.
In American football, the 6–2 defense is a defensive alignment consisting of six down linemen and two linebackers.