Barcelona and Napoli are currently struggling, I think Napoli is way worse. But In the Champions League, teams often find a different level of motivation and performance, and past struggles in domestic leagues might not necessarily carry over to European competitions. Barcelona have legacy and rich in the Champions League, with multiple titles and memorable performances that suggests an ability to rise to the occasion in crucial matches.
Champions League brings out the best in everyone is a crucial point. I think Barcelona is more familiar with this tournament that give them advantage in mentaity aspect. Both Barcelona and Napoli will be hoping to recover before their matches in February. This is the importance of the period leading up to the fixture, where teams can address their issues, regain form, and approach the Champions League clash with renewed confidence.
For round 16 Barcelona can still be relied on I'm sure they will qualify for the next round but after round 16 we don't know which team will be their next opponent if the next opponent is a club from the Premier League then Barcelona will be kicked out basically, Barcelona will find it difficult to go further. The thing that concerns us is that next January the transfer window will open each team can bring in new players who can change their strengths while the champions league will resume in February this means our predictions today can change and be irrelevant for the next 2 months. who knows, Barcelona might bring in a new player to replace Lewandowski because this player is considered irrelevant.