Napoli must have been the happiest in this matchup because they know the Italian teams very well and they haven't lost this year apart from Lazio and Inter. I'm sure they will leave Milan out of the champions league. Milan, on the other hand, should be very upset to be paired with Napoli because Napoli are currently one of the strongest and in-form teams not only in Serie A but also in Europe.
Without a doubt this is bad news for Milan, when facing a difficult opponent a classic way in which you can level the playing filed is with the surprise factor, so if they were facing a team from a different league then this could be a tactic they could use, but this is not a tactic they can use against Napoli as they know them like the back of their hand, and as such if the chances for Milan to win this game were too low to begin with, now those chances are even lower as Napoli is not going to fall for any of their tricks.