I'm gonna go that one of them scores a knockdown that should be ruled a slip in a round there winning giving their opponents 3 more points than they should have at the end of the round
Found this: The referee for the bout has not yet been decided but the NSAC are expected to make an announcement this week. Kenny Bayless and Tony Weeks have emerged as the front runners to be given the nod. http://www.mirror.co.uk/sport/boxing/mayweather-vs-pacquiao-referee-300m-5510931