Some injuries, like penalties, are related to not having good enough players, players that aren't fundamentally sound, aren't executing, don't have a clue what they are doing, or are trying to do too much. For example, if a play is well blocked, the runner will run past his lineman, deliver a blow to a defensive player, and drive him backwards. On a bad team that can't execute, a defender may come crashing down the line of scrimmage, smear the running back, and drive him awkwardly into the back of a lineman's legs, blowing the lineman's knees out. Another example, would be an upback in punt formation that forgets that his primary job is to block the punt rush, and instead sprints away from the rusher giving the punt rusher a free release and a direct beeline to annihilate the punter and/or block the kick. If blocked properly, the punter doesn't have to worry about having his plant leg ripped out from under him like a dry stick.