Recently we've played 3-4-3 with these exact players. But i feel Koeman will place De Jong in the midfield for this game because there is possibility of a slow midfield of Pedri and Busi getting schooled by the trio of Kroos-Casamiro-Modric. De Jong in midfield will be crucial.
Would guess it will be same line up again or at most Araujo in for Mingueza at RCB.
Have said previously think Pedri and Busquets wont be quick enough to get to Modric/Kross and they will be switching play out wide to fullbacks/wide players all game.
They will target space in behind Dest and Alba any time can.
FDJ is the best midfielder at Barca by far but taking him out of defence causes a whole change of system and would need to be more of a traditional back three which cant see Koeman opting for. More likely switch to 433 later on in game if Real dominating midfield.
Although to be fair they could dominate midfield and get caught on break in this set up.. if Dembele has scoring boots on.