What it is

A prevent defense is a soft, deep coverage with extra defensive backs, used when the defense wants to avoid giving up a long pass or big play.

In a game

It is used late in a half or a game when the defense is ahead. The defenders stay far from the line and let the offense gain short yards while the clock runs.

More detail

Critics say the defense can give away easy short passes and let the offense march down the field. The idea works only if the clock is nearly out, which is why it is used in the final minutes.

Animated diagram

1. The defense is ahead near the end of the game, so it does not want to give up a big play.
2. Only a few players rush, and the others drop far back in coverage.
3. The offense can complete short passes, but the defense stops long gains and lets the clock run.