4–3 defense
American football defensive formation / From Wikipedia, the free encyclopedia
"4-3" redirects here. For the TV screen standard, see Aspect ratio (image) § 4:3 standard.
In American football, a 4–3 defense is a defensive alignment consisting of four down linemen and three linebackers. It is called a "base defense" because it is the default defensive alignment used on "base downs" (1st and 2nd downs). However, defenses will readily switch to other defensive alignments (such as a nickel defense or a dime defense) as circumstances change. Alternatively, some teams use a 3–4 defense.