Does he play polo on a polo field, or in the basement of his home?  If it is not his principal place of business, or a place where he regularly meets with other team players and horse trainers, I don't see how he qualifies.  (Nor do I see why he's being paid on a 1099 and not a W-2, like most athletes.)  You might be able to call some of it a travel expense, but it's difficult to make the case that it is "ordinary and necessary."