the rule should be simple and clear! The offense controls the clock. If the defense usurps that control for any reason, it's a penalty. Carry the injured player off the field! It's a penalty! Carry the player faking an injury off the field, it's a penalty! If the player with a broken leg wants to come back in the next play, fine! BUT ONLY AFTER THE PENALTY IS STEPPED OFF! THE DEFENSE CANNOT TAKE CONTROL OF THE CLOCK WITHOUT SUFFERING A PENALTY!