Agree completly with your points that context does matters, but as much as comparisons are important to understand the skill level of a player, there also needs to be an intrinc value that holds true by itself. In this case, what we know of what makes a good PG defender and what his responsibilities are, one the main responsibilities is stopping penetration and keeping your player in front of you. Keeping a player in front of you is fundamental to all perimeter defenders.
I disagree. No pg always keeps his man in front of him, and no pg ever has. The only way to really judge them is to compare how often they do it compared to others. What if I said thar Ray Allen is a terrible 3 point shooter? Can you really show whether that's true or false without comparing him to other players?
This problem of Rondo was well illustrated during the playoffs, I really don't see any need to contest it.
On one hand, that wasn't necessarily Rondo at his best. They played every other day without a break, he led the league in minutes per game, and he re-injured his ankle in the Chicago series. On the other hand, he wasn't as bad as people make him out to be. People here were watching his play closely looking for errors. Do that with any player and you'll see flaws in their games.
And yep, you're right about me being able to clarify what I meant... I just don't think that in this instance there was any need to do so because I don't know how anyone can still think of Rondo as a good penetration stopper. And since I consider that one of the most basic and important defensive elements in the perimeter, I can't in good conscience say that Rondo is a really good defender as many are lead to believe.
Again, though, "good penetration stopper" and "really good defender" are relative terms. You could be saying that Rondo's defensive skills are poor compared to his passing and rebounding skills. You could be saying that Rondo's a poor penetration stopper compared to the better pgs of the 80s. You could be saying that Rondo's not as good as he could be. But you don't seem to be saying that he's poor at it compared to other pgs that are currently in the league, which is what I'd use as a measuring stick.