I think what makes Ginobili so effective is his "awkwardness". He's a lefty, he has those long shifty strides, and his shot looks weird and is difficult to block. By no means would I consider him athletic but he does have great body control especially in traffic. I think Hayward is more athletic and could become a much better defender...not sure if Hayward will ever attain Ginobili's level of expertise at flopping though.
