There would be no rules though. Pretty much every Chimpanzee attack results in the human getting mangled, but that might have to do with the fact that the human is not anticipating the attack and is hit by surprise. If the human were to keep the chimp at a distance and outsmart it, he might have a chance(albeit a slim one)
The rules are in your mind.
Have you ever been in a fight?
You will only punch someone's face while punching someone's throat is a lot more effective in many situations, but you will not do that.
Ever fought someone who is really, really angry?
That guy will do anything to inflicht as much pain as possible.
Think of the chimp as a really really angry guy, with the upper body strength of a body builder and the speed of a small child.