I don't think you are making any sense with your argument. Are you thinking of Allen and Sahin as the same type of player as Lucas? Lucas is defensive oriented while Sahin and Allen are more offensive. He is playing further up now because we now play with a higher defensive line but that doesn't mean he is required to make forward/offensive passes, that responsibility belongs to the 2 other midfielders playing alongside him. Think of Lucas as Busquets, Sahin as Alonso, Allen as Xavi. Busquets was never the creative playmaker, all he does is recycle possession by passing it to the more creative players and shielding the back four, nothing fancy. Do you think Barca's system would work without Busquets? Have another look at Real Madrid, they too need Khedira to shield their defense. It is suicidal we were to play 4-3-3 with Gerrard, Sahin, Allen or Shelvey in the 3 midfield positions, why would anyone play 3 offensive minded midfielders when we are already playing with 3 strikers, that leaves the defense extremely exposed. Look at how United are struggling with their defense without that holding midfielder since Fletcher is out.

Yes, but the mould and role of both Allen and Lucas are entirely of a different DNA.

Lucas' is based on the primera volante role of the Brazil's 4-1-2-1-2, whereas Allen's of the 'main dictator' in Swansea.

Both roles differ even if their passing is a main component in both roles, and purposes (of delivering)

I am not seeing the logic as to WHY should we even think about offloading Lucas?