It is undeniable fact, indeed Barcelona performance improvement when it was take over by Xavi their having a good progress, but when Xavi plays against big clubs outside La Liga, he doesn't have perfect tactics. Today also in a friendly match against Arsenal, Xavi lost tactically although it was a friendly match but Barcelona shouldn't lose. But anyway I shouldn't underestimate him, Xavi might be able to make a surprise in the UCL later because now the Barcelona squad have a new better players.
Losing to Arsenal was not supposed to happen, not after adding some crucial players to the team this summer. Furthermore, there are certain good numbers of targets ought to be reached this season. Xavi Hernandez will restrategize and implement new game structure, because the blaugrana becomes very weak towards elite clubs outside their league. Barca always dominate games within La Liga but are not giving the same energy in other top competitions, that's their weakness, comparable to PSG in Ligue One. Their ultimate target is the UCL title, I doubt if they will make it to the knockout stages this time.