Powe's a proven NBA player; Diogu is not, he's a guy who has gone from lottery pick to trade throw-in. Powe's hurt, sure, but he should be back well before the playoffs. If they decide they can't chance it that Powe can contribute, I can deal with that - IF his roster spot goes to someone who can help.
Didn't we learn anything from The POB Experience? While it's not an absolute, more often than not when a guy's not gettting ANY playing time, there's a reason (more often being "he's not any good" than "his coach is an idiot").