Those absences will see Memphis Depay continue to lead the line, following his summer move from Lyon, with the Dutch international having hit two goals in his first four La Liga appearances for the Blaugrana.
Without Dembele and Fati, Phillipe Coutinho and Yusuf Demir could again take the wing spots in a front three.
With crucial midfielder Pedri ruled out through injury, Sergi Roberto will likely keep his place in the midfield trio alongside Frenkie de Jong and veteran Sergio Busquets.
While deputising for the injured Jordi Alba, left-back Alejandro Balde was also forced off with a back issue last time out, leaving no fit senior left-sided full-backs in the squad, meaning Sergino Dest may have to move across with Oscar Mingueza coming into the right-back slot.
Experienced centre-back Gerard Pique will be keen to return to the starting XI, after he was used off the bench last time out, while Ronald Araujo's late equaliser against Granada could be enough to keep him in the side.
Barcelona possible starting lineup: Ter Stegen; Mingueza, Araujo, Garcia, Dest; Roberto, Busquets, De Jong; Coutinho, Depay, Demir