With the rule changes put in several years ago and the way teams have exploited them, you really need "switchability" more than anything. That's what makes Green so effective. He can basically guard all 5 positions, he can handle the ball, he can rebound, he can shoot the 3, whatever. It's not like positions have vanished, but the centers and point guards have kind of converged towards the middle. So you can play a couple of interchangeable guards without a pure point guard, and you can play a couple of below-7-footers in the frontcourt without a traditional center.
This is one reason that I think a pure "rim protector" is overrated. Look at Timofey Mozgov, a guy that many of us here on this forum were pining for for years. The Cavs often times choose to play without him, even though he's one of the best pure shot blockers in the league (whom they gave up two 1st-round picks for). Why? Because on defense, you can expose the hell out of him in the pick and roll as a guy who's slow footed, can't switch onto smaller players, can't hedge on the perimeter and run back to the paint, etc. And on offense, he can't shoot long jumpers and isn't a greaet ballhandler and passer.
Food for thought as we think about centers we might draft in this upoming draft. Mickey already does a lot of the things you need in a modern NBA center, perhaps better than a lot of the guys coming into the league right now.