That's right, a busy match schedule will be a major challenge for Napoli, while pressure from their main rivals will also increase. However, I think Napoli is well prepared for next season competition, as Conte has improved the depth of his squad.
Inter Milan, Juventus, and AC Milan will be Napoli main rivals for the Scudetto, while AS Roma, Atalanta, Lazio, Fiorentina, and even Como have the potential to be a dark horse team.
AC Milan should be able to take advantage of the momentum well, as they are focused solely on domestic competition. Their quest to bounce back and challenge for the Scudetto should be easier.
The chances do seem easier for AC Milan and several teams not competing in other competitions besides Serie A. However, AC Milan must also have sufficient squad depth for this. To win the Serie A title, every team must be able to perform more consistently in all matches to avoid any rivals blocking their path to the trophy. As we saw last season, Napoli was able to overtake Inter Milan at the top only because Napoli was able to be more consistent in every important match.
One of the biggest reasons was that Inter, who played longer in Europe last year, appeared more tired on the pitch than Napoli. Those who played more were tired, and Inter unfortunately lost the league. Napoli won the cup, but if Milan want to win this year, they need to improve their squad size. They need to have plenty of alternative players.