KG's back up is the most glaring question.
There are other concerns but the roster seems to have enough depth to eventually answer them.
Not so at center. Hopes rest largely on the shoulders (and heart) of Wilcox. How quickly he gets up to speed, if indeed he does return to an approximation of his former self, will be key.
Milicic would not be in the league were he not 7'0" and 275 pounds. This signing was a reach by DA, a desperation move. Although Milicic will likely play more he is basically suited to the same role as Jason Collins.
Jason Collins is the insurance policy.
Fab Melo is the future. I love the pick and think by his third year he will emerge with value. That said, selecting Melo begat Milicic and Collins who are basically anchors at the end of the roster.
After Wilcox, the best hope lies with Milicic rounding into form as a servicable back up to Garnett. I actually think DA may have seen something of Perk in Milicic - someone who could play some post defense, pick up a couple of garbage baskets, grab a couple boards and generally protect the paint. IMO, that's asking more than he can give.
What I expect we will see is Melo forced into action before he is ready. He will have the defensive presence needed... in time.
The only other option is to trade for a decent back up. One of the guards, Milicic / Collins / Wilcox and or possibly Joseph as the bait? Not sure that we could expect enough back?
Rajon Rondo, Phil Pressey
Jerryd Bayless, Chris Babb
Jeff Green, Chris Johnson
Brandon Bass, Jared Sullinger
Kris Humphries, Kelly Olynyk, Joel Anthony
Colton Iverson (stashed overseas)