Most teams when they go young / rebuild end up being terrible (really terrible) that year. If you look at teams like Sacramento and Washington you'll get the idea.
But, there is one thing about the Celtics that might save us from that horrendous fate.
If you look at teams like Washington and Sacramento, they went out and brought in young guys like Nick Young, Jordan Crawford, Andray Blatche, Tyreke Evans, Demarcus Cousins, etc. Guys who has potential, but were flagged as high risk due to their rough personalities.
There is also another thing those teams usually lack - an Elite star player with playoff experience.
The thing I like about Boston's "rebuild" is that first of all, the three young guys we are planning to build around are Avery Bradley, Jared Sullinger and Kelly Olynyk. Those three guys are as good as it gets when it comes to personality - great work ethic, intense desire to win and willing and eager to lean.
To add to that, Sullinger and Olynyk are two of the most fundamentally sound rookies that have come in to the NBA in years. Watching them on the court the are both incredibly active, always moving, setting screens, making the right pass, great hands (they both seem to catch anything that comes near them) and great footwork.
Offensively, but Sullinger and Olynyk can score inside thge post, and both have range out to the three point line. 7 footers with three point range are a nightmare to defend (Dirk, Rasheed, etc) so Olynyk has the potential to cause all sorts of problems for opposing teams. Sully helps to make up for his rebounding limitations as well.
A lineup of Rondo, Bradley, Green, Sully, Olynyk has to be (mentally) one of the best units out there. None of those guys would have problems with touches, would have issues getting along with other players, would have problems with effort or desire to win. Rondo likes to take charge and be listened to, and I think Bradley, Green, Sullinger and Olynyk are all very coachable players who will work with Rondo rather than against him - I think they will look up to him and see him very much as a coach on the floor. I think that will take pressure off the new coach as well.
I'm not saying this team will be great, but they might not be as terrible as people think. We have a clear cut All-STar (and top 3 in the NBA) PG in Rondo, a volume scorer who (can shut down elite opponents SFs) in Green, an elite perimeter defender in Bradley, an excellent rebounder and inside scorer in Sully, and a 7 footer with three point range. All of these guys have incredible work ethic.
It's really more the bench I'm worried about.
Firstly we have no pure PG, although I was pretty impressed with what I saw from the little guy in summer league (sorry, forgot his name!). With Rondo coming back god knows when from his injury though, we need a backup PG who is good enough to start for a few games. Terry would have been nice...but Danny probably didn't want to force the guy to play for a rebuilding team. Until we find a PG we are screwed.
Secondly our backup SG's are Courtney Lee (who was useless last year), Jordan Crawford (disaster) and Marshon Brooks (slightly better version of Crawford). I'm hoping that Lee will return to form and be a very solid backup SG, though I'm not holding my breath because he was terrible last year. Here's hoping he gets along better with the new coach and comes up well for us. Brooks is a SG with mental issues but who could have pretty nice upside if he got his head together. Crawford is pretty much the same player, only even worse than brooks in pretty much every way (I'm guessing he'll go).
At SF we have Gerald Wallace (while rediculously overpaid) is actually a pretty decent backup SF. HE was poor last season, but if he returns to some of his previous form (even a hint of it) he could be one of the better backup SF's in the league.
At PF we have Bass (a borderline starting calibre player and a very good backup PF) and Shav who is a hard working who can hit the boards, defend inside and score down low.
At Center we have Fab Melo (who looks much improved) and Colton Iverson (who looks like he could contribute right away with rebounding and interior defense).
Aside from PG and maybe Center we actually aren't looking that bad.