I think a more interesting question might be simply "are we underachieving or are achieving about what this team should be achieving?".
I think we are one player away from being the 55 win team that many think we are the underachieving version of. We need a starting PF and that will improve or starters and provide additional front court depth. A team like Detroit kills us. San Antonio's bench bigs killed us.
Horford, Amir, Olynyk, and Zeller just isn't enough.
I still don't buy this narrative that we overachieved last year and are achieving about where we should be this year.
There's clearly a lack of defensive intensity from last year. I think our starting unit defense is much worse than it was last year, which is surprising given our upgrades in personnel. I think we just focus way too much on trying to outscore the opponent rather than stopping them. Some of this can be put on Amir's significant drop in play, but IT, AB, and Jae have all performed significantly worse defensively than last year, and adding players like Brown and Rozier into the rotation also hurts our D.
Boston is only giving up 2 more ppg than last year which when you consider the injuries to Crowder and Horford, isn't bad at all.
Given the injuries 10-8 is a pretty good spot for Boston to be in.
Oh, I agree we're in a decent spot for the injuries we've had.
And perhaps with more time together as a healthy unit we'll get back to our defensive ways. But as it stands now, we're just not the same defensive team that we were last year, and our priorities as a team seem to have shifted dramatically.
But you are ignoring the injuries in your analysis. Since Crowder came back in the first Detroit game, Boston has had the following results
Wins while giving up 92, 93, 92, 104
Losses while giving up 109, 121
The 104 win was without Horford. The 109 loss was the 3rd best team in basketball and was a 5 point loss. The 121 was obviously last night against Detroit, but Boston is always going to struggle a bit against a team with a guy like Drummond in the paint (and Boston got killed on the boards 52-33), and thus that is more an aberration.
But the thing is last year Boston gave up 102.5 ppg good for 13th in the league (scoring 105.7 good for 5th). Thus far this year Boston is giving up 104.4 ppg which is 16th (scoring 105 which is 12th). When you consider that Boston lost Horford for 10 games, Crowder for 8 games, Olynyk for 6 games, and Smart for 3 games, it doesn't really seem to me that Boston has lost much of anything (aside from some rebounding without Sullinger). Boston was a mediocre defense last year and is a mediocre defense this year, however Boston was a near elite offense last year and this year is mediocre. That seems to be the bigger concern.