Barcelona have also been inconsistent this season, especially in the LaLiga, but mind you that every match in the CL RO16 is going to be tough, i understand that some teams are underdogs when you compare them to their oppositions, but in the two games you highlighted above, neither of those teans are underdogs, it is going to be a 50-50 game that anybody can win. Barcelona and Arsenal are very much beatable, and it would be a mistake to write off Napoli and Porto.
Napoli and Barcelona this season do not look as good as they did last season, but as we remember, Barcelona in the last Champions League could not even get out of the group, this season they were more lucky with their opponents, but now they are weaker, so compare them with Arsenal is difficult. Porto remains a dark horse, but I would still classify them as a strong middle team rather than a top club.
The match Between Barcelona and Napoli is going to be 50-50. Both Barcelona and Napoli have been looking inconsistent in their performances. Barcelona will be in the 4th position if Atletico Madrid wins their next game and Napoli is in the 5th position.
But it's the Champions League and it brings the best out of every team. I would say Barcelona will have an edge in this match as they are a club with history and their fans will push them for victory. Key players from both teams need to perform. I would say this is the only pair up in the UCL which will be a 50-50 in round of 16. This is going to be very exciting on both legs.