He was in Madrid for a basketball camp when a Spanish reporter asked him if Kobe Bryant was the best basketball player in the world-- a belief widely held throughout basketball circles, except Inglewood evidently.
Not only did Pierce claim that he was the world's top baller, but he went as far to say why Kobe should not be considered the best. And Pierce's reasoning did not have anything to do with Kobe's on-court skills. It was more about Kobe's ego than his game.
Check out the interview posted on Red's Army: http://redsarmy.wordpress.com/2008/07/29/the-spanish-interview/