Reasons to believe in a victory:
1 - Napoli will have a much easier game ahead of them against Verona, they will be able to spare some players and if they lose they won't mess up the Italian championship, unlike Milan who have an important game against Bologna to defend their position to qualify for next year's Champions.
You have to also consider the position of Verona I know that they are at the bottom of the table and may want to try to move from the last three teams in the league.
2 - Napoli will play at home
It still may not change anything.
3 - Napoli only lost 3 games in the Italian championship, they are a very hard team to beat, and I don't believe it will happen again, even more in sequence.
Of which AC Milan was one of the teams that beat them.
4 - There are good chances for Osimhen to play, he is an important reinforcement.
Just back from Injury, he may not play and perform as expected.