The last two seasons have been a nightmare for big teams like Barcelona and they probably don't want that to happen again in the Champions League next season. As a coach Xavi is fully responsible for the performance of the team he has built and as long as they can still prove their capacity then they will probably be much better later.
It is not about what they want or don't want, it is about their ability to play well and achieve good results. Barcelona have been playing worse in Champions League after losing Messi. But previous seasons, when they had Messi, all responsibilities were blamed on Messi unfairly. Now they have to pay the cost and accept the fact that their squad is not actually good and competitive, with or without Messi.
It's very natural that after losing Lionel Messi, Barcelona seemed to have lost a leader on the field and that was clearly felt. Even other players such as Sergio Bosquest and Jordi Alba also could not restore the confidence of every player. I think barcelona should have prepared for that and there's no way they will continue to rely on just one player. On the other hand, they also have to develop more and with a new squad, all the legacy of their seniors must continue with the same mentality. Maybe it's not appropriate for a team like Barcelona to experience this continuously and I think they have to break this bad result in the Champions League this season.