Xavi in Barcelona was very impressive and I couldn't expect to see Barcelona winning the La Liga title when he started working there because Xavi is not experienced as other coaches. However, in last season Barcelona couldn't play in the champions league but I think in the next season when they are racing with other teams like Real Madrid and Machester City, they can even have the chance to win the champions league title if we see the same performance from this team in the next season.
With the same performance they won't win the Champions League. Compare the 10 best games that Manchester City played in all competitions with the 10 best games that Barcelona played in all competitions last season. The difference in performance between the two teams will be massive. Barcelona played four very bad games in the group stage. The first game and then the second game in the group against Bayern was alright not bad. In La Liga they played well because of their defense, but they also benefitted from Real and Atletico Madrid to struggle so much.
It will be a new try for them in the Champions League and at first they should think about passing the group stage and nothing else. Talking about the Champions League win before the season even started isn't really making any sense.