I agree Fan33. There's plenty of reason for hope.
The kid was 19 and he broke his foot one month before his rookie season. He couldn't contribute immediately so he was sent to the D-League. Big deal. A lot of decent centers did nothing during their first two years. Dalembert did nothing for two years. Biedrins did nothing for two years. Perk also didn't look too impressive his first two years. Jermaine O'Neill did nothing for four years. So, it's a little ridiculous to write off a young 7 footer. He's admitted he was immature. If anyone can get through to him, the Celtics can. If not, it's a very low risk signing.
It's no surprise he didn't work out in Nelson's system. What was his role? Go out there and make plays? Dominate? The Celtics are going to drastically simplify his role on the court. KG and Thibodeau are going to tell him exactly where to stand. Rebound, give the ball to Rondo, go up court and set a high pick, and get the heck out of the way. With enough repetition, in a limited role, he could be effective.
He doesn't come in with the expectations of a high pick as he did in GS. He's a back-up center. Five to ten minutes, 3 rebounds, 3 points, 1 block, defense and 3 hard fouls on Howard, Dalembert, Horford or O'Neill. Keep Perk and KG out of foul trouble. That's all we need. In Nelson's system, that would be failure. In our system, that's success.
Will he succeed? I have no idea. But it was a very shrewd signing on Danny's part. I'd rather have a young guy with upside who might be a washout than a mediocre 30-year old retread. I'm sure Ainge was well aware of O'Bryant's limitations in GS. If Ainge didn't believe the Celtics could turn that around, I'm sure he wouldn't have signed him.