Napoli will continue to keep their lead even if Milan equalize the points this week. But I don't even wait for Napoli to lose points against Sassuolo.
So far, Napoli is really doing very good performances. Every time, they could play their best in the match, whoever the opponents were. Their performance so fa has been very consistent. In the next match, they will fight against Sassuolo. From the paper, Napoli should have a bigger chance to win. I am also exactly sure that they will not face a hard match. However they will play at home, so this will give more pressure on Sassuolo. The point difference between Napoli and Milan is 3. They must do their best in order to keep their rank up or they will be beaten by others.
This condition is exactly different from Juventus. In UCL, Juventus has failed tin the group qualification. This season, their performance is very dropped. Fortunately, in two matches previously, they could win over their opponents. And here, they must make more victories again in the next matches in order to rise up their points. At elast, they can be qualified for the next Champion League season.