Johnw1104 on 26 August 2017
I have to think this would be just about the biggest upset I've ever seen if McGregor won, so I'm going with Mayweather.
The few examples we have in the past of fighters dabbling in other styles suggest that they generally get their ass kicked. Even Anderson Silva had to throw in the towel (literally) when he boxed a rather average boxer a back in the day, and I really don't know any MMA fighters who were craftier than him. Of course, he'd later win a boxing match, but this is basically the greatest MMA fighter ever and he was certainly not fighting anyone close to Mayweather.
