He only knew what he saw from Kabuto. He didn't know Naruto even possessed Sage mode nor did he know anything about the frogs having it as well.You must be registered for see links->You must be registered for see links->You must be registered for see links->You must be registered for see links.
Please note Sasuke knew of Senjutsu as did Naruto. This is Naruto going against Sasuke in analyzation and winning.