The centre-backs are not just slow, they seem positively lethargic.
However, I imagine that this inadequate setup will be addressed by Emery, piece by piece, but I expect that he wishes to take the dressing room (and the fans among others) along with him when he makes changes, and to have sufficient evidence for a compelling, incontrovertible case for change.
While I think Cech's days are numbered, it will be interesting to see whether Emery persists with him until, say, Hallowe'en.
Certainly, I would expect to see some of the new signings given an outing before too long, and it will be interesting, too, to see who is eased out (and bought in) over the course of the next transfer window, as that should reveal how the manager is thinking, and what areas he thinks need attention.