He will be a starter once he's fully fit and understands what flick wants from him.
He struggles being a single pivot, and while flick starts with a double Pivot, that's really only on paper, because Pedri is always high up the field and casado as to stay tactically discipline to cover the spaces.
But he shouldn't just walk in the team the way Casado is playing.
The good thing about him, is he can play both roles in midfield.
Basically a starter/rotation, which will be the case for all our midfielders once everyone is fit.