most immobile midfield in all of European football history? 
Palencia is injured.
also, Masche won't travel with the team.
Theres no chance Sergi and Semedo will both start since we dont have a back up RB.
If one of them gets injured, the other one can be reassigned to the RB position. And we bring in a midfielder from the bench. Semedo should start at RB, Roberto should start in CM. Rakitic on the bench.
Interesting to see Oriol in the squad. Hopefully Valverde doesn't pull a Lucho and leave him on the bench the entire game when he could have been playing a tough game with Barca B.
That's exactly what he will do

Interesting to see Oriol in the squad. Hopefully Valverde doesn't pull a Lucho and leave him on the bench the entire game when he could have been playing a tough game with Barca B.
He has called 20 players, 2 of them are Barca B players. So there is actually chance that he doesn't even make it to match squad.
He is probably gibing him some experience with 1st team training etc
PS: If Mascherano didn't travel then 19 players in squad and one will be removed