The rest of the Eastern Conference has made great strides.
They've all drastically improved, and we've gotten worse. It should be basically impossible to say that the Bobcats, Raptors, Wizards, Cavs, Pistons, and Magic haven't improved and that we haven't gotten worse.
2 things - Hungry young players that are looking to have break-out seasons (John Wall/Beal/Porter, Kemba/MKG, Valanciuanas/DeRozan, Kyrie/Waiters/Bennett, Knight/Drummond/Monroe, and Harris/Harkless/Vucevic) and really good veteran free agent signings (Josh Smith, Big Al, Andrew Bynum).
And what did we do?...
Wake up and take off those green goggles - if you think we have better talent or a better team structure, you are going to be very disappointed. From a glance, you can tell that our bigs are going to be completely abused this season. People act like our back-court defense will make up for it - did it make up for it when KG was off the court? Defensively, the center is the most important position in basketball. Realize that KG gave our guards a lot of confidence. They could play as aggressively as they want because KG would always be there to help them. KG's gone now, and the offensive talent pool we are going to be facing down low is substantially higher. We are going to get destroyed in the paint.
You're underestimating the effect of a strong perimeter defense. By far our worst weakness defensively has been penetration and needing stepping up from our bigs to defend it, leaving his man in the process.
In fact, if I told you that Bradley last season had 3 units who played over 100 minutes together, and that of those 3, the one with the best performance (both offensively and defensively), by far actually, was one that featured Green as a PF and Bass as a C, would you believe it? I'd say you wouldn't, and you would be wrong.
In fact, that was the most productive unit of our whole team throughout the full year.
I think what occurred with the Celtics last couple of years, how good Memphis is defensively, is proof enough of the impact that good perimeter defense has. Marc Gasol just won Defensive Player of the year, and this dude doesn't rebound defensively all that well, and is certainly no shot blocker (good defensive awareness though). And this is with Zach Randolph who's not winning any defensive awards any time soon.
So you can be skeptical of our roster and how it can play defense, but please I exhort you to not degrade perimeter defense unnecessarily.
The thing is that to have good perimeter defense, you need more players involved to make it work. When you ask for good interior defense, you can usually manage with just the one player... which distracts from the value of what each brings to a team.
As it is, the Celtics should have strong perimeter defense, and hopefully rebounding, and that should lead to being a good defensive squad, even without the presence of a shot blocker in their midst.