A nickel defense puts five defensive backs on the field instead of the usual four. The fifth is the nickel back, and he almost always replaces a linebacker.
Where the Name Comes From
A nickel is five cents, and the package uses five defensive backs. The same logic gives us dime, which is six defensive backs, on the reasoning that two nickels make a dime.
Why It Exists
Offenses started using three receivers on most snaps. A base defense with four defensive backs has to cover a third receiver with a linebacker, which is a mismatch the offense will attack all day.
Swapping a linebacker for a defensive back fixes the coverage problem at a cost: the defense is now lighter against the run.
It Is No Longer Situational
Nickel used to be a passing-down package. It is now the most common personnel grouping in the NFL, played more often than base defense, because offenses use three receivers more often than not.
That has changed how teams build rosters. The third cornerback plays more snaps than the third linebacker, and is paid accordingly.
The Nickel Back’s Job
Usually he covers the slot receiver, which is the hardest cover assignment on the field: the slot man can release in either direction, so there is no sideline to help. He also blitzes more than outside corners, since he lines up closer to the ball, and has to tackle in space against screens and quick throws.
It is a distinct skill set, which is why some players specialize in it rather than being a converted outside corner.
How Offenses Attack It
By running. A nickel defense has one fewer linebacker, so heavy personnel and downhill runs find lighter boxes. That is the entire logic behind offenses using two tight ends on early downs: force the defense to stay in base, then throw.
Related
All football positions · Cornerback vs. safety · What a blitz is
The Bottom Line
Five defensive backs, one fewer linebacker, better against the pass and lighter against the run. Once a situational call, now the default.