I just dont see Itachi beating Nagato anymore. Nagato is just too OP for him.

Animal Path
This alone would drain Itachi. Itachi would need strategy and caution to take out the bird, cerberus, ox, rhino, chameleon, saaaaadpanda and crab.
-Nagato would be safe from Tsukiyomi and Totsuka Blade while flying on the bird shooting Shinra Tensei's and rocks while the cerberus, ox and rhino attack Itachi on the ground. Itachi would need chakra technigues such fireball and bolsom crimsom nails to take out the grounds summonings.
-Itachi would drain himself using 2-3 Amaterasus to take out the bird and cereberus but Nagato still has the chameleon, saaaadpanda and crab.
-The Chameleon would camoflauge his chakra and Itachi would need to get rid the chameleon but remember..NAGATO IS INSIDE THE CHAMELEON AND THIER VIVSION IS LINKED. Any water and fire technigue aimed at the reptile would be absorbed by Nagato making hiim even more dangerous.

Preta Path
This path basiclly makes all of Itachi's chakra technigues useless. However, Nagato cannot absorb amaterasu or so I dont believe he can.
-As for Susanoo, NAGATO CAN NOT INSTA-SORB IT AS ALOT OF HIS FANS CLAIM. He can only absorb a little at a time since Itachi wont just stand there.

Asura Path
-This path makes close range with Nagato suicide. He'll just wrap Itachi in ropes and use preta path to absorb his chakra, human path to rip out Itachi's soul and naraka path to consume it.
-However, Nagato risks Tsukiyomi at close range.

Human Path
-We all what this does and Nagato risks Tsukiyomi with this.

Naraka Path
-Only good for extra fields of vision.

Deva Path
-This path would drain Itachi like no other. Itachi's needs susanoo to be safe from Bansho Ten'in but that sets him up for preta path. Itachi would use more chakra to fix it but it would drain him.
-Chibaku Tensei is Nagato's last resort and the problem is people think Itachi can destroy alone while others believe he cant. If he can, Itachi can use the smokescreen to use Totsuka Blade. If he cant, then he is doomed.
-However, ITACHI WILL BE TOO DRAINED TO DO ANYTHING BY THE TIMES THAT HAPPENS.

You all still think Itachi could win?