Huge difference between playing Riquelme at AMC and Wijnaldum. Koeman has to be specific about the lineup he wants and the tactical roles he see's as the days of having someone sit in the AMC and do nothing are over- much like the days of the sweeper.
If Messi is starting then it has to be up top in a Firmino-esque role which activates the overlaps of Dembele and Ansu. Otherwise the defensive structure is going to be lost.