A knockout tackle in football is a very hard and forceful tackle that seemingly 'knocks out' a player. At the very least, the player that has just been tackled ends up in a daze due to the collision with the tackler and subsequent impact with the ground. Knockout tackles often result in a penalty on the defender for unnecessary roughness and can cause the offensive player to leave the game with an injury.
Knockout tackles often occur because the defender is not using proper form on the tackle, as proper execution in which the defender wraps up the ball carrier generally do not cause injury. Listed below are a number of potential mishaps on the defender's behalf that can result in a knockout tackle:
Any excessive or negligent maneuver that leads to a knockout tackle is subject to a penalty for unnecessary roughness or illegal contact. When a defender is flagged for one of these two penalties, the ball is moved up 15 yards from where the penalty took place. Two fouls for unnecessary roughness by a defender in the same game results in an automatic ejection, and referees also reserve the right to eject first-time offenders if a knockout tackle is deemed intentional or truly obscene.