Xavi is still trying to continue that Tiki-taka style of play and i dont see where this plan is heading to. If Barcelona stick to that outdated game pattern of Tiki Taka they are likely to suffer more losses.
It is not out-dated and Manchester City are playing another variant or upgraded tiki-taka. Issues in Barcelona are their players are not at world-class like when Xavi is core of their squad and tika-taka. Don't blame this defeat on Xavi. Remember when Messi was here, Barcelona was destroyed more terribly by Bayern. Give Xavi and Barcelona time to digest this defeat and come back.
Xavi cannot be blamed for Barcelona's defeat. Barcelona's squad is very weak and inexperienced compared to other title-seeking squads. We can't expect much from such a team. Xavi has taken charge of the team. He will now stabilize the team somewhat. Fix their gameplay and strategy. Then next season if Barcelona can take some star players in the team then maybe they can be strong. I don't expect much from this team until new players are added.