There's a difference between self-confidence/ego and arrogance ... Rajon is not arrogant, but he has the same kind of self-confidence that Larry Bird had. If you had asked Larry if he was the best at his position at the height of his career, he would have answered the same way.
The great thing is that they are/(were) both driven to be even better, always keep improving, and very open-minded about taking constructive criticism/instruction from those they respect and have great knowledge of the game. I can't wait to see how far Rondo can go if he remains healthy, and just what heights he'll reach in his career.