I agree with you, Napoli condition can not be compared to that of Barcelona this season anyone can argue about it but the league standings is a typical examples between the form of the teams. The truth is that Barcelona is the bigger team yes but they are also in better for this season judging from their performance and position in the Spanish La Liga table on like Napoli that has been struggling since the beginning of the season to win matches both in the league and champions league, I think the injury of Barcelona won't stop them from progressing ahead of Napoli especially in their hom ground.
Barcelona has a higher chance of winning the match, even though several key players are injured. The second leg will be held at Barcelona headquarters, which will certainly benefit Xavi squad. Napoli experienced more ups and downs in performance than Barcelona, their position in the Serie A standings is a reference that they are very inconsistent, and failed to finish in the top four of the standings. Barcelona is still in the top four in La Liga, and has a big chance of appearing in the Champions League next season. Barcelona winning percentage was quite high in the second leg, Xavi had to formulate a strategy so that his team could win easily.