First of all, the celtics beat Miami without Rondo. To disregard that game as beating a quality opponent is being ridiculous. Second, regarding the rest of their opponents since Rondo's been out, the celtics can only beat the teams on their schedule. To use that argument of weak opponents as backing for stating blatantly and confidently that the celtics are not championship caliber without Rondo I think is being narrow-minded.
"Waiting to reserve judgment" like Chris said or saying you "need to see more before I'm fully convinced" are appropriate things to say. But I think that criticizing a team for the quality of teams on its schedule since Rondo has been out is wrong.
I think the celtics have a chance at the championship. I like the basketball I'm seeing out of them. I thought we were championship caliber before Rondo got hurt (although werent playing like it at the time) and I think that while his loss was huge, I've seen so far and am envisioning a continuation of other player stepping up and filling in that gap (while not completely, still a large part of it).