Zizic and all those other stashed kids will most likely never play a minute for the Celtics. I know we all like to hype up these kids, but let's face the facts - They just aren't that good. And they never will be.
You really don't know what you're talking about. Zizic would likely go in the top 12 this year - top 15 max (as reported by the Sporting News, O'Connor and other sources). He's got talent, he's big and he's young. Zizic isn't a 2nd round, #50 stash here. He's a talented guy who have proven himself against good international competition. He just finished 2nd in the EuroLeague Rising Star trophy (past winners include Andrea Bargnani, Danilo Gallinari and Ricky Rubio).
He'll play this coming year. What he won't do is start. But he can come off the bench, grab boards, throw around his 20-year-old-but-still-NBA-ready body and generally take over Zeller's role. And that's enough for me this coming year. Too many Celtics fans think either a pick has to be an All-Star or it's a total bust. Zizic probably won't be an All-Star but he's the kind of big man who could have a long and productive NBA career.
Yabu is a slightly different case. China isn't known for their talent and his foot injury won't help get him ready for the next level. I still expect that he'll be on the roster next year but may not see the court (or have an extended stint with the Red Claws). But if he can learn to play defense, his 38% 3 pointer will help him find the court especially if Olynyk is gone.