I heard a couple of people say this, and after watching more closely I completely agreed:
The biggest myth right now being spread by Celtic fans is that Posey is our best defender versus Lebron. Forget about who you THINK would be the best defender (like I did for a while), and actually watch what is happening on the court. What you'll see when you do this (if what has happened in games 1-6 continues into game 7), is that Posey not only gets eaten for breakfast by Lebron every time he tries to guard him, but Pierce is actually holding his own against the King. And that's not to say that Lebron always has success when Posey is on him. Often times Posey gets bailed out by Perk, PJ, and KG.
I still think Posey is a great defensive weapon for us to have. In this series though, Lebron is owning him.