What it is

A sack is a tackle of the quarterback behind the line of scrimmage before he can throw. It loses yards for the offense and makes the next down harder.

In a game

Sacks come from a fast edge rush, a blitz, or good coverage that gives the rusher time to arrive.

More detail

A sack is recorded as a statistic for the defender, or shared between two defenders as a half sack each. A sack that forces the ball loose is a strip-sack. Sacks are as often the fault of coverage or of the quarterback holding the ball as of the offensive line.

Animated diagram

1. The quarterback drops back and looks for an open receiver.
2. The defensive end beats the left tackle with speed and goes around the edge.
3. He reaches the quarterback before he can throw and tackles him behind the line of scrimmage. That is a sack, and the offense loses yards.