A tackler, loosely speaking, is not allowed to push an opposition player in the back during a tackle. By the strictest definition of a push, any contact from behind could be considered a push in the back, so the rule is usually enforced under only the following three circumstances:
- If a player is bent over or on his knees, usually to win or protect the football, and an opponent knocks him over from behind.
- If a player is lying face down on the ground, and an opponent falls onto his back, intentionally or unintentionally. The first circumstance often directly causes this second circumstance also.
- If a tackler pursuing a ball-carrier uses one or both hands to push him from behind, causing him to be knocked off-balance as he attempts to dispose of the ball. A chaser often attempts this when he sees that the ball-carrier is about to kick the ball, and he is not close enough for a tackle.