Just as in the case of a hockey player who was prosecuted in Canada for hitting another player over the head, the issue is intent. Hitting a shot at another player is indeed part of the game and would not ordinarily carry any liability, criminal or civil. However, if you had said "I'm gonna hurt you" or given any other indication just before doing it that your wish was to cause injury or pain, you could be arrested, sued, or both.
"Where's the REST of me?"
Ronald Reagan, in "Kings Row"