While Barcelona being the favorite during the second leg should not surprise anyone that watched the first leg, at the same time it should be worrying that the only clear opportunity Napoli got ended up in a score, so Barcelona cannot attack recklessly during their upcoming match or Napoli could seriously punish any mistake they make on defense and get a surprising win that no one expected.
One clean chance and it immediately led to a goal for Napoli, it was like confirming that Barcelona's defense was fragile so that the opponent could create goals despite creating minimal opportunities. I think if Napoli are in a very good state they will be able to beat Barcelona in this first leg match. On the other hand Barcelona can create a lot of opportunities but they always meet a dead end so that every time they attack it is a lot of missed opportunities.
Anything can happen in the second leg later, and I'm sure Napoli will look different in the second leg later, because there is no other option for them to come out to attack, yes of course at the risk of creating gaps in the defense. Actually they can play total defense to bring the match to the penalty shootout, but that is also risky because with the continuous attacks it will be able to make them tired and at that time usually the focus will be unstable and that might create another gap for Barcelona to create goals.
If we look at the results of this first leg, Barcelona should not underestimate Napoli even though Barcelona will play at home and will get full support from their supporters. Napoli can do something surprising if they are not careful with Napoli, especially since they also have good attackers who can convert opportunities into goals.