Also worth pointing out: while Rondo garnered some All-Defense awards playing with KG, his defensive level has been well below Westbrook's over this last season. I'm not sure that you can just wash your hands of that quite so easily by saying "well he's not healthy yet," since the disparity was pretty substantial over the regular season, despite both of them coming back from injuries and being subject to rust.
http://bkref.com/tiny/5sa2c
Rondo's defensive rating this year was indeed not good. In 998 minutes of play, opponents scored 1.122 points per possession.
But it's interesting to note who he had on the floor with him.
His most-used 5-man units all had Jared Bayless as his backcourt mate. That combination accounted for over a third of Rondo's minutes (373) and gave up a pretty awful 1.181 points per possession.
With Bradley as his backcourt partner (324 minutes) their defensive rating was 1.092 points per possession. Over 100 possessions, that's a 9 point swing.
Now, lest you think it was just a case of Bradley making Rondo look good, it's important to note that the back-court pair of Bradley and Bayless was also bad at 1.116.
None of our guard combinations had particularly good defensive ratings this year - but a large part of that has to do with how awful our interior defense was. If you select down to using our at least nominally good defensive front court of Green+Sullinger+Humphries, then the RR+AB defensive rating was a fantastic 0.903 points per possession. Simply swap Humphries out and Bass in, and it was a dramatically different 1.084!!!
Basically, the huge variances in our lineups and their varied performances throughout the year make trying to say definitive things about player defense very difficult.