It's a great question. It seems like anybody can beat anybody in it. I've seen Rick Roufus get the crap kicked out of him and then kill the same guy the next fight.

I think it's mostly because they always have grand prixs where they fight several 3-round fights on the same day so if you're beat up from a fight it'll affect you in subsequent fights to the point where you can't even continue. It's like whoever takes the least amount of punishment usually wins the event.