I think Napoli are still quite superior this season in defending the Scudetto trophy because they have a squad that has hardly changed drastically in this transfer window. So their mentality is still strong enough to provide a strong competition for their challenger team.
Their winning mentality have already been sharpened by the introduction of new players, coupled with the experienced ones they have on ground. Their last match have proven that they are above the others clubs and have a real advantage. If they are able to successfully defend their title this season, we may see them take on a bigger challenge - the UEFA Champion's league and actually be one of the strongest teams.