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.
I can say Barcelona have good odds than Napoli because both team have proven to be stronger and watching them play in their perspective league this weekend was totally dissapointing, Napoli held a draw while Barcelona struggled to score a goal making it 1 nil victory against their opponent. These are elite team and they're not obligated to be facing challenges this season. Thinking about or it more coincidence, Barcelona and Napoli lifted the league title last season but this current one comes with a whole lot surprises on both ends.
Barcelona decides about the result of this game, but remember that in the first leg it was quite a typical Barcelona game. They were the better team, had the better start into the game and several chances to get ahead with two goals, but then they conceded that goal because of a brilliant Napoli attack and afterwards Napoli suddenly had all the chances to win that game. Barcelona literally forgets the game plan when they concede a goal and it is not the first time this season. So if Barcelona keeps control over the game most of the time, I guess they will be the winner or at least have bigger chances. But if Napoli can score a goal, it's probably going to be almost equal chances for both teams.