Here is something that I hadn't consciously noticed about Gary but I can see now that its been pointed out by Bill Simmons (and his dad):
And he's had a dramatic effect on Pierce. As my Dad pointed out after the Portland game, there were two or three times when Pierce was ready to go into PPSM (Paul Pierce Sulk Mode) and GP sensed it, so he yanked Pierce aside and pulled his head back into the game. You can't put a price on this stuff.