I'm not real impressed with Rivers the coach or the player.
Doc was a better player than he is a coach by a substantial margin, in my opinion.
I offer this purely as an empirical statement with no editorial comment intended. Doc wasn't great, perhaps, but at his peak on those Hawks teams that had the epic playoff battles with the Celts in the 80s, he was very good. Bird had great respect for him. I remember Larry saying something to the effect that Doc would have been even better if he wasn't such a nice guy.