I feel Pep would 've brought along Bartra nicely, seeing it was he who gave the youngster his debut at the Vicente Calderón, and then his subsequent starts. Pep was a believer of his talent, Tito isn't (atleast thats the msg he has sent out so far). Tito doesn't strike me as a risk taker with the youth, as opposed to Pep who was quite visionary and big promoter of La Masia, and wasn't afraid to throw them in to the thick of action, experience or not. The former did/does play Montoya and Tello, but them both had already featured under Pep for the first team in some toughies. I doubt Tito would just take a youth defender and debut him at a hostile ground like Pep did. Though he could prove me wrong in the future.
The sane thing to do would be to do away with Fontas, JDS, Bartra by next summer. And then go for a CB of Tito's choice, preferably summer, as it will be hard to find quality due to the dynamics of the winter transfer window. I hate how young talent(world class or not) is wasted on the bench, when they should be playing to rectify and fine tune their game at this juncture of their career.