the numbers show that we're better offensively with rondo, but worse defensively with rondo. the defense improves by a noticable margin when rondo is off the court.
Here's the thing though, the only reason we're better offensively without him is that we get more offensive rebounds when he's off the court. The OReb% difference is 19ish to 24ish, that's an effect of Sullinger's minutes given that he's the only Celtic who is an effective offensive rebounder.
Go take a look, our eFG% is higher with him on the court, our TOV% is lower, and our AST% is higher.
In previous year's Rondo's never had such a large OReb% differential, and usually he improves our offensive rebounding due to his own skill at it.