so you're trying to tell me that the Petra Path would absorb a blow from the Sakenagi (totsuka's sword) ??? ... NOPE!as does every one in the leaf village and pain still pwned them
Itachi's 3 best tech's will not help him so he is screwed
tyuskiomi (hello i am tourtuing a corpse for 1 second that can't feel pain and does not effect the other bodys)
ammaratsu (preta path adsorbs it shinra tensei repells it)
sussano (Shinra tensei sends it flying, gedo mazo sends its dragon's right though it, chibaku tensei crushs it)
end of story immpossible for him to win
Shinra tensei, and Chibaku tensei getting through the Yata mirror??? NOPE!
One swipe from the sword and all the Pain Paths are gone... It would probably send Nagato into a coma considering that he controlled the 6 paths... Or just leave him all alone as 1 path...
Plus as I said, Itachi has never used even 1/2 his strength except at the end of his fight with Sasuke (which was only to prepare his brother for the future)