There has been a huge spotlight shined on our center position since Perk was traded, and the general narrative either way has been that the Perk/Krstic swap was a defense-for-offense exchange. I've made similar arguments, suggesting that the swap was a good one because Krstic would open up the offense a bit without the Cs losing much on defense. Well, so far I've been half-right.
Here are our 5-man units on the season including Rondo, Ray, Pierce, KG + one other big man (from basketballvalue.com).
Interestingly, it's not the defense in the Krstic unit that is really suffering...in fact, so far the defense looks very similar to the unit with Perk this year and much better than it looked with Semih. Instead, it is the offense that has been putrid. A lot of this can be tied into the struggles of Rondo, the other big story around here since the trade.
In the end, I think the low offensive output is more of a fluke than the reasonable defense. Almost every defense that we've sported with our Big 4 and a big man over the last several years has been good, and none with legit minutes played have sported offenses this terrible. I'm still looking forward to the return of the O'Neals, because the line-up of the Big 4 + Shaq has been and will be our best unit overall. But I'm not ready to completely write off Krstic as a legit starter for us...the team as a whole has been playing poorly, but odds are that their level will include good defense with much better offense than what they've shown to date.
Also of note, the Big 4 + Green unit has been great on offense but lesser on defense. The minutes are limited, but this matches more with intuition and previous experience. The Big 4 + Wallace and Big 4 + Posey line-ups in recent years also had trouble defending as well but were solid offensively. When we go small, that seems to be the way it works for this team.