A softball batter was struck with a pitched ball directly in the orbit of the right eye and fell immediately to the ground. The physical education teacher ran to the player to examine the eye. There was some immediate swelling and discoloration around the orbit; how ever, the eye appeared to be normal. The player insisted that he was find and told the teacher that he could continue to bat. After the game, the teacher told the athlete to back to his room, put ice on his eye, and check in tomorrow. That night the baseball player began to hemorrhage into the anterior chamber of the eye and suffered irreparable damage to his eye. An ophthalmologist stated that if the athlete's eye had been examined immediately after injury the bleeding could have been controlled and the athlete would not have suffered any damage to his vision. If the athlete brings a law suit against the physical education teacher, what must be prove to win a judgment?