To be honest, if he's that much of a player I'm sure he's used to dealing with girls who are attracted to him. If you tell him you like him he probably won't blush and mumble and never be able to look you in the eye again. Has he had girlfriends before? If so, what was he like with them? Is he the type of guy who would be monogamous if he met someone special or is he just not a relationships person?
Also, whilst you say you're physically attracted to him, are you sure it's not just pure lust? Do you think there is a deeper connection?