I have a slightly different opinion than you. I think the Barca and Napoli pair is quite unpredictable; they are the reigning champions of both the Spanish and Italian leagues. Currently, the form of both Barca and Napoli is not good, but when they face each other, the result is hard to predict. Napoli's style of play remains challenging for teams from England and Spain. Therefore, it's not easy for Barca to overcome Napoli in this round.
When you look at the performance of this two teams, it is very obvious that they are on the same level now. Their individual performance in both leagues is just the same and nothing much can be said in their upcoming match against each other. One of this two teams will be eliminated from this round and won’t advance to the quarterfinals, the thought of it makes it more interesting to watch out for their match by next year when they meet in the round of 16.
Barcelona is currently not in a good situation, otherwise, a team like Napoli could never beat Barcelona with the performance they had during the last season with their coach Xavi, but since there are many injured players in this team and there are many players who left the team, I think this can be hard as you said to predict this match.
I think Napoli can have a good chance to score a goal in this game if they have Osimhen in the good form because the defenders of Barcelona have not performed well recently.
I believe Barcelona's current situation is more about finances than Xavi's or the team's tactical prowess. Their financial problems arent new, but their debt is forcing the sale of important players. Team performance is affected. This is showing in their defensive flaws, which Napoli, especially with Osimhen in great form, might exploit.
Barcelona's difficulties against Almeria suggests deeper issues than injuries or player transfers. Financial issues dont go away quickly, and Xavi is struggling to manage them. Any coach finds it difficult to foresee matches like the one against Napoli. Im curious how they'll handle these stormy times.