doubt it, he couldn't hide behind those big puffy boxing gloves nor clinch and hide from getting hit, and Mayweather isn't exactly what you'd call a power puncher either LOL, many fighters have proven that against him, the last one being Hatton who ate tons of punches trying to close the distance
the UFC has proven time and time again that boxers get beat quite easily, even good ones
bare knuckles no holds barred fighting isn't boxing, totally different game
they wouldn't have to get him on the ground at all, muay thai clinch and its game over, Mayweather would spend the whole time running away like a little girl