The Napoli we saw last season can comfortably beat the current Barcelona team, but it's quite unfortunate that the Napoli we are seeing now are just a Shadow of the last season team. This match is going to be keenly contested. Both Barcelona and Napoli are not doing very well in their respective leagues. Both Napoli and Barcelona can advance to the next round so it will be difficult to determine who will qualify.
The Napoli vs Barcelona match is still quite far away and both of them still have time to improve their performance in January because both of them can take advantage of this time to change all their current shortcomings for the better. Because in general these two teams are not doing well right now so they have to make a lot of improvements in each line of players in order to recover from the bad performance they have experienced so far.