Are you kidding? Nazr is in no way a better defender or shot blocker. I think everyone's forgotten about Rasho just because he got hurt and Pop didn't want to change things up halfway through the playoffs. Rasho did a great job defensively for us through the season. Offensive rebounding, you have to give Nazr an edge, but only because he's more aggressive and over his man's back all the time. I don't know how he didn't get called for more over the back fouls in the playoffs. Also, a couple inches is a BIG deal. But it's not just the height, it's also the bulk Rasho brings. I'd feel a lot more comfortable with Rasho guarding Shaq than Nazr.
If we trade Nazr, Rasho starts and he's not overpaid. If we trade Rasho, he starts somewhere else and is not overpaid. Sure he's overpaid when he's riding the pine, but something has to change at some point, we're not keeping both for years to come. Rasho is a STARTING center, somewhere.
As for Oberto, we're not even debating great yet. Let's see if he's even good first. If he were better than Rasho or Nazr, he would've been in the NBA long before now. But he's never played a minute in the NBA. I don't know if he can play good defense and rebound against NBA players. I don't think we need a great center, but I do think we need a decent one. Does Oberto qualify as a decent starting NBA center? It seems a bit premature to decide that, but apparently you already have.