Great start, still worried about the lack of size, which I believe has correlated to the drop in defense and is clearly responsible for the rebounding deficit (and it is nearly a 5 rebound swing from last year). Rob will certainly help with both of those, but I'm not sure he will make up the whole difference. The team has also been pretty healthy (obviously aside from Rob and Gallo) in that guys that normally miss 15 or so games haven't missed very many yet (Brogdon is the only guy that has missed a string of games in a row and that was just 4).
I've paid more attention to this since you brought it up in previous posts, and I've come to agree with you on this. As a general rule, more size = better defense. That size has to be somewhat versatile to defend spread NBA systems, but it does matter.
I think Brad Stevens knows this too, which is why we keep hearing rumblings that he's looking for more size to add to the bench.
Kornet, Griffin, and Vonleh can all give you some minutes in different matchups. They may not be as productive as you'd like, but they can hold their own.
But I'd like to get another productive big man with size that can play the 4-5. Ideally, he could play next to any of Williams, Williams, or Horford if we needed him to, but that may be a lot to ask for with our current trade assets and matching salaries.