I'm not sure if McKay starts immediately. For one, it could take him (like Nader) some time to get up to game speed, find his role, develop the chemistry with team, etc. But maybe not. He's being touted for rebounding and as a rim-protector - which is an instinctive skill. My guess is that it will depending on the other team's post-players.
At this point, you'd have to think maybe Hogue sits, as he's in a serious rebounding funk. But who knows - by the time Dec 20 rolls around, he could be playing like a man possessed again, and Naz could be trending down. Either way, it will be great to have McKay available, and I think it's easy to see there will be an 8 or 9 man rotation most nights - Edozie being the 9th guy.