I wonder if we really just need to stop thinking about this team (for now anyway) as having a best XI.
I didn't see loads of pre season, but it seems to me part of the reason it was a little disjointed is Mikel was trying different combinations to see how they worked. It's entirely possible, especially with this coach, that we will land on a preferred XI and that players like Saka will likely start most of the time even if we don't. But part of having the squad we have now is that some really top players are going to be on the bench occasionally and sometimes they may even stay there.
Whatever team is put out tomorrow is just the one Mikel thinks is the right one to win this particular game.