Wow... give the guy a break.
I think our expectations should be tempered a little bit. He's got the physical tools, and he can defend in the post. He's got good fundamentals, although he's not Hakeem. The Celtics don't need him to score. Put all these things together and you have a backup Center playing for the vet min. Great signing on paper.
Then, reality will check in and we'll see what Darko can give to the team. If he can give Defense, hard fouls and some blocks, that's ok with me. If he can make some basket playing off KG, Pierce and Rondo, that'd be sweet. If he can get in game shape and show his solid post game, that'd be excellent.
He'll be better, without a doubt, than Mikki Moore, Ryan Hollins, Paddy O'Blount or Troy Murphy.
He'll surely be better than Stiemsma, JO(due to his injured self), Semih Erden or Scott Pollard.
He could be better (as a backup C) than Big Baby, Nenad Krstic or PJ Brown.
The Celtics have only had 3 Centers in the last 5 years that are out of his league: Rasheed, Shaq and Perk.
Rasheed (although only in the playoffs) brought the best post defense of this era, because he could defend the Dwight Howards of the world (like Perk but not as well as him), but he also could defend the Bynums, Boguts or Kamans. And he was unstoppable in the post. But Sheed, as bright as he was, wasn't reliable.
Shaq was good on D, and incredibly good on offense. But he couldn't last.
Perk was a beast (he seems a different player now) defending the post, but he struggled against Centers who could shoot over him (Bogut, Bynum...). On offense, he just made some dunks off passes, or putbacks. He tried to play in the post, but he couldn't score. The best thing is he was reliable and played 100% every game.
Now, Darko could bring almost everything that Perk brought, but he's 27, and it's not very probable that he improves his defense, although he'll look better alongside KG. He's a better offensive player than Perk, but he hasn't shown desire and commitment to bring his A-effort every game. The fact he's rejected more money from the "european Celtics" (Real Madrid is the team with more european titles) could mean he's trying to make a statement.
There's a chance in a million that everything falls in place, and he matures and buys into the team culture, and suddenly he plays 100% to his abilities. Probably it won't happen, but even if he keeps playing the way he's played last year, he can help our team, and he deserves a chance from the fans.