Board Thread:Versus Debates/@comment-26958911-20151010214426/@comment-26636534-20151018150930

@Sicus

Jiraiya, as stated before, has been gathering intel on the akatsuki for years and knows for a fact that Itachi is one of their members. So he should know about Itachi's abilities, he even encountered Amaterasu, sealed it and knew he'd have to find Tsunade to heal the damage done by the Tsukuyomi, so he knows about MS powers. As for the flying Susanoo, Itachi hasn't shown to be able to use Complete body Susanoo so I don't think you can assume that.

The speed of Amaterasu has been shown to be inconsistent so it can't be called instantaneous, also all of his MS techniques come with severe backlash, so stamina will be an issue for Itachi, but not for Jiraiya.

Due to his research, Jiraiya probably has a way to counter Itachi's speed and other powers since he knows about it. The only thing that would really surprise him would be the Tosuka Blade and the Yata mirror along with the Susanoo. But don't forget about the toad chant genjutsu, which Itachi is susceptible to even in his Susanoo.

As previously stated, Itachi himself said he'd probably lose to Jiraiya and at best would kill each other, even if Itachi had reinforcements, so the odds are more like Jiraiya wins 9/10 times.