There are so many ways that situations like this can occur and I think each of them has really interesting dynamics. There are so many people involved in so many different capacities and all of them are each taking different risks.
In the case that a fan is bringing a suit against an athlete, if it's anything like the game referenced here, where the offending action is outside of the context of the event, then yes, I think the athlete should be subject to prosecution. If it's within the context, then obviously the athlete is liable.
I think athlete vs. official and official vs. athlete are very interesting. I remember the Browns lineman a few years back who brought a suit against the referee whose flag hit him in the eye and ended his career. I don't know if the player brought the suit against the official or the league, but I think that's legitimate because throwing the flag in such a way was an unnecessary, and--now we know--dangerous action to take, no matter how fluke it was. I think there is a definite barrier between officials and athletes in ALL sports, even baseball, where any injury done by one party to the other could be looked at by a court.
The most interesting dynamic though, and I doubt we'll ever see, is Player vs. Player. I just think that athletes by nature want to be the toughest, fastest, strongest, and best, but I don't think many of them want to have to prove it in a court room. I think a great percentage of the modern athlete would allow their egos to keep them from bringing suit against each other. Also, I think there is a certain code like Chris says where you're never intending to hurt someone. Even in a hockey fight, boxing or MMA I think the vast majority of athletes would say that their intent is never to hurt or to cause injury, but the nature of the sport just lends itself to injury and within the rules of the action, nothing would be taken to court. And hockey fights, though they are against the rules, are part of the game, and there are certain rules for conduct there, as well.
I don't know how the court deals with "unwritten rules" though.