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 it involves the UEFA Champions League matches, there are clubs we know that they're 100% serious and competent to face their opponents, be it elite or a club that's inferior. Napoli new coach, Walter Mazzarri is starting to develop the club to become one of the prominent clubs that shoots faster and higher scores to qualify, but Barcelona can just win the lucky star by winning. Napoli might not be in good stable shape at the moment, the exact thing happens to Barcelona but I actually think these teams can actually fixed themselves up and running.