It's a tough situation because on the one hand, Green was hired as a rookie coach and I think coaches can improve just as players can, and if he sticks around he might be excellent in a few years - he's already done the most important thing, which is getting the trust of the players.
On the other hand, how long is it gonna take for him to figure out some of the very basics of timeouts, substitutions, and rotations? Three years should be long enough to know basic stuff.