I wouldn't completely rule McGregor out. Obviously the most likely result by a huge percentage is a dominant Mayweather decision, but Conor does pose some interesting threats to Floyd. He's bigger than Floyd, is incredibly quick, has strange movement that Floyd will not have seen before in a boxing ring, and the power in his left hand can put anyone down. If, and it's a big if, Conor lands that left hand he could knock Floyd out. It's unlikely, but certainly not impossible when you've got a guy as talented as Conor. Floyd's also 40 now, and it'll be almost 2 years since he last fought when this fight comes around, that could definitely play a factor.