Tommy Lawlor, in a well-argued column critiquing Juan Castillo:
I’ve been re-reading parts of Bill Walsh’s brilliant book Finding The Winning Edge. He talks about the need for a coach to be an expert. He must be so thoroughly trained that he knows everything that’s going on and can coach/teach the players appropriately. I don’t doubt that Juan understands the role of all 11 players and can theoretically explain things. The problem is that I don’t know if he can teach those concepts well.
It’s worth noting that this applies across Andy Reid hires. When he has brought in a veteran coach like Mornhinweg/Mudd/April/Washburn, those went well. When he promoted Castillo/McDermott/Segrest, things didn’t work out. Current defensive assistants Mike Caldwell and Michael Zordich likely fall into the latter category.