Defensive midfielders –

Sergio Busquets (first-choice) : The youth product has solidified his position in the first-team. But he is still susceptible to fatigue. Ernesto Valverde should retain him for the important league games and the Champions League.
Paulinho (second-choice) : The new signing needs time to settle into his role. Valverde should hand him some starts in the Copa del Rey and the Champions League. But if he gets injured, Barcelona will lose the backup defensive midfielder.