Really, In anime, the good guy gets his ass kicked in the first 90% of the fight but somehow pulls it off in the end. Yet people are calling Naruto weak based off Sai's comment. Really, What was Sasuke's opinion of Naruto? He was weak. But even said he was wrong during the rescue arc. What was Gaara's opinion of Naruto? Weak What was Kiba's opinion of Naruto? Weak What was Neji's opinion of Naruto? Weak What makes you think Sai is going to be any different? Naruto overcame all of them, he will overcome Sai. If Naruto surpassed everyone else, it would become too lopsided and Naruto would win every time. Really, the Sai arc isn't going to be much different from any other arc. He will slam Naruto for being weak, kick Naruto's ass for the most part, but lose in the very end.