To be honest I think he should retire, he already won as much money as he wanted was one of the best and now he must concentrate in other things, this seems like a matter of honer to me since he was robbed in the last fight but there is not a guarantee that he is not going to be robbed once again.
Many rumors out there that this will be his last fight and after winning or losing this match his on his way to politics, focusing in it. Move on mate, that last fight's decision won't change, a lose is a lose and this is the chance that he can correct those judges decision by knocking out Horn. Do you even think what if the fight will be on Australia again and Manny knocks him out?