It is still very possible for AC Milan to defend the Scudetto title this season as long as they can play consistently and win one match after another. It also depends on Napoli's performance, if Napoli declines in terms of performance and loses point after point then that will increase the chances for AC Milan to take over the position now occupied by Napoli. But with Napoli doing well so far, I have a feeling they won't miss the excellent opportunities they have now. Napoli are 8 points away from AC Milan and it will be very difficult for AC Milan to catch up, especially since a big game awaits them in the second half of this season.
To catch up and shift Napili's position is indeed very difficult for Milan to do, At least they need eight points to win and Napili must lose to reduce their points but it is impossible to let Napoli lose on purpose, Napoli have the upper hand and are only a few steps away from enjoying their victory in the Serie A league.