Do you honestly believe that Simon's numbers have (and will) come down because he has regressed as a player - meaning that he has become a worse basketball player - and that that regression is the fault of the staff? Because I think his role has changed and that he's accepted that change and that's a credit both to Simon and to the staff.
You touched on something that I've been pondering. I believe Simon is at his ceiling, and his numbers are more indicative of a change in his role than him regressing. If you compare his offensive numbers 7 games in last year, he is pretty much in line with those numbers, FG% and PPG. Where I see the impact is APG going down from 5.7 pg to 2.9 pg and TO pg going down from 2.4 to 1.6. Which all makes sense as he does not have the ball in his hands as much. But his role change shouldn't have impacted his presence on the defensive end as much as it has, especially with Keita out. They need his rebounding, shot blocking, and steals. That is effort. So maybe Simon hasn't accepted the change and that is were its showing. Time will tell.