I think it’s mostly a small sample-size issue. I’ve seen concerns here posted about the lack of someone to replace Rob, and while that’s true to an extent, last year the Celtics allowed 43.2 points in the paint per 100 possessions. This year it’s 43.8, so that’s not a meaningful difference in 4 games. On the other hand, teams are shooting 40% from 3. Some of this may be due to scheme (we’re having Horford play more drop coverage than he did last year), but a lot of that is just luck and isn’t sustainable by opponents. People may want to point to second-chance points, where we’ve fallen from giving up 12.8 per 100 to 15.3, but again, through four games that’s a pretty small sample size. Our DREB% is higher this year than last, even after the game against Chicago.
Where we do miss Rob (and where I don’t think we could have acquired a viable replacement because he was pretty unique in this) is our ability to defend the mid-range. Rob could cover so much ground that he really closed off mid-range jumpers. We don’t have anyone who can do that now, but there are few in the league as capable as he was on that. Mostly I think we’re just not applying the same level of ball pressure as we did last year, which helps create these openings, and I think that will be fixed before long.
It is a lot easier to pressure the ball when you have someone down low that can defend the paint if the guy you are pressuring gets around you. That is where not having a shot blocker can cause all sorts of problems to your overall defense. You are correct that very few can defend the mid range (and the interior) like Rob can, but there are guys that can defend the paint that are available and I believe that would help a great deal with the overall defense. You need a guy that can defend the rim and make it difficult for people driving to the hole. Boston doesn't have that without Rob, but could as there are several big man shot blockers still available.
It's easier, but the Celtics have a bunch of good wings and guards that don't need that extra support.
Again, it's sample size. The Celtics are currently 2nd in the league in FG% at the rim. Last year they were 6th.
Currently teams are shooting 52.6 % from 10-14 feet against the C's. That would be a record, by several percentage points, if it held up. (No one's ever even allowed 50%).
Teams are shooting 55.3% from 15-19 feet against the C's. That too, would be a record by several percentage points (again, teams always allow below 50%).
Teams are shooting 50% from 20-24 feet. Yet again, that would be a record.
All of those numbers are going to come down, because it's a four-game anomaly. In none of those stats, which again would be full-season records by wide margins, are the Celtics currently the worst in the league. Weird things happen to teams over four games.
The at-rim numbers are going to get a little bit worse. The mid-range and 3-point numbers are going to get a lot better, even if the Celtics do nothing differently. That doesn't mean there aren't some adjustments to make, and with 4 days between games after a 3-in-4 stretch on the road, one should expect some adjustments.
