Cushion is the amount of space a defensive back puts between himself and the receiver.
Cushion is easiest to see at the beginning of the play, but the term also describes the room that a receiver is given during the play as well. It is a relative term in that there is either very little cushion being given or there is a lot of it.
Above is a lot of cushion; here is the opposite: very little.
Giving cushion or not is a tactical choice and is not right or wrong. The advantage to giving the receiver cushion is that it is harder for the receiver to run by the defender or get to the deep part of the field, making big gains less likely. The disadvantage is that it is more difficult to defend short, quick passes.
Giving less cushion is better for defending quick passes, but it has the trade off of making it more likely the receiver can get deep or break a big play.
Defensive philosophy, situation and defense all influence how much cushion is given. For instance in a Cover 3 defense a cornerback may have responsibility for covering a deep zone. It would make sense for that corner to give the receiver some cushion so that he can get to his zone before a receiver does.
Situations where the offense has fewer yards to gain usually dictate less cushion. On 3rd and 3, it is inadvisable for the defender to be 10 yards off the ball.
Defensive philosophy also plays a role. Defenses that want to be aggressive often provide little cushion, while those that are more cautious and concerned about denying the big play may give more cushion.
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