Four of them are midfielders
FC Barcelona is suffering an injury per match and over the last days they have lost Messi, Iniesta and Rafinha. The low of Iniesta during the match vs Leverkusen is even worse because not many players can replace him. Xavi left to Qatar and Arda Turan won't be able to play until January, so Luis Enrique has difficulties to complete the squad.
With this panorama, the coach called 6 Barcelona B players that joined first team in the morning's training session. Four of them are midfielders: Gumbau, Babunski and Cámara. The other two are defender Robert Costa and forward Aitor Cantalapiedra. The session was done under heavy rain in Barcelona.
It's quite probable that Luis Enrique include some of these players in the squad list to face Sevilla this Saturday. Right now 6 players are injured: Bravo, Vermaelen, Adriano, Iniesta, Rafinha and Messi. Without being able to count on Arda and Aleix Vidal, only 16 first-team players are available.