Rocky Marciano VS Earnie Shavers. Who wins and how?

Just out of interest Magnassakki - from the point of a big heavyweight with a good deal of experience sparring with some of the best heavyweight of recent years - what's your thoughts generally on Rocky Marciano? How do you envisage it being in there sparring with him - apparently he never really 'looked' that great in sparring ever? What do you see in him in general from the point of view of someone who's mixed it with the best in the business?