I don't even know if either of them will actually play.
If we are playing a 4-5-1 formation, I would think that Didi would be playing along with Xabi and Stevie. But if it's a 4-4-1-1 thing, where Kewell could actually be the one behind Cisse or Baros, then maybe both of them won't even get to play.
That's the way I think would work - the 4-4-1-1
---------Dudek------------
Finnan-Carra-Sami-Djimi
Kewell-Stevie-Xabi-Riise
------------Luis-------------
----------Djibril/Milan------
with Stevie picking up Kaka's runs - don't think either Didi or Xabi really have the pace to do this - and either Kewell or garcia in the 'hole' keeping Pirlo busy - that leaves Xabi free to switch the play for Riise and Kewell (RM) (which will stretch the Milan mid-field that likes to play narrow) and Djibril/ Milan making runs and creating space for Luis to run into - sorted.
However, probably be completely different...