I'm shocked there's anything to debate about here. The quote is discouraging, plain and simple.
Rondo in a nutshell the past season "I played no defense, let AB, Smart do the dirty work, made KO , Sully look bad".
Let's all be honest - it doesn't take much to make Sully and Oly look bad defensively. They do that just fine on their own because they're not very good defensive players. There's a reason there's a ton of trade ideas where we receive a defensive minded center to "pair" with either Sully or Oly.
As far as the original quote - I'm sure he'll be asked to further talk about what he meant/clarify at some point before the game or postgame. What I think he meant - and this is my opinion, I'm not declaring it as fact - is that he didn't play on ball defense at the point of attack very much. If you've watched any Dallas games since he's been there, they've basically asked him to play AB's role - applying full court pressure, being the main guy to defend opposing points and allowing Monta (a pretty solid steals guy) to basically play free safety.
I think you are correct.
When I first heard about the quote (not in Rondo's voice), I was sure that this was Rondo doing a dead-pan, sarcastic, "Yeah, I played no defense for the last 2 years". His MO has been to frequently use straight-faced sarcasm. However, after hearing the quote from Rondo's mouth, I don't think it was sarcasm. On the other hand, to think that he meant literally that he hasn't played defense in two years, is absurd. You watched -- he played defense.
What Rondo seemed to mean is that over the last 2 years he did not play defense at the same intensity level as he had in the past, or as his "younger" teammates are doing in the present. I took it to mean that his focus was on running the offense and preserving some energy on the defensive end. It does protray a changed and less assertive approach to defense than in previous years. And it does indicate a purposeful let-down in defensive intensity -- reduced effort by design. However, in the context of recovering from his surgery, and in the context of maximizing his more essential role on the team, he decided to let the young guys provide the bulk of the defensive intensity.
This doesn't absolve him as I do think he IS saying that he let up defensively for the last 2 years. And in the context of asserting that he is now defending at a higher level with Dallas, we are left to conclude that he could have been defending at a higher level when he was here. BUT, let's not blow this out of proportion by taking a literal interpretation of his words. He said he didn't play defense for 2 years and we all know that this comment is not literally true.