They are still a young team, which explains their current situation. Barcelona haven't stabilised yet and progressing with such a situation is difficult. Barca fans may feel uncertain about this team, especially if they look at Barca back-line.
Their problem is that they haven't found Pique's replacement. Pique is already 35 years old and his physique has declined. Even Pique always has a hard time facing a striker who can run quickly. I think Xavi should start thinking about the central defender. I think he should be brave to start the rotation,for example by installing Kounde as the starting line up. Because Xavi is carrying a mission of improvement and he deserves to give more playing time to the younger defenders.
If not for the current number of injury cases I don't think Pique would be starting for Xavi team. He is aged and a little sluggish now which is noticed when he plays and playing against an attack with good and skillful players with good pace what would you expect from Pique? I expected to see a rotated squad in the game but it seems Xavi was not courageous enough to make the big decision and we saw how it turned out to be, Real Madrid outclassed them.