I think Slot likes his core team and will play them. Regardless of who else is available. Some positions will see more rotation (Gakpo/Diaz, Robbo/Tsimikas, Jones/Szoboszlai).
There is an argument to say that a settled first 11 will read each other's game better. Less running than last year should certainly help too.
Feyenoord minutes per player.