I'll rephrase for sake of your reading inconsistency: Nagato has no canonical knowledge of the
Inner workings nor possesses a counter for Itachi's Genjutsu; Tsukuyomi. Nagato had poor control over the Gedou upon summoning it as opposed to Mokuton wielding Obito and Madara as it rampaged and immediately deprived him of the two elements it was missing being, life force and chakra. It attests to the reason why he never summoned it again (as it would take his life) which means such a matchup depends on his physical state. Bear in mind time there is a forced time limit using this technique.Such an emotional response would be
highly unlikely at the beginning of a fight. During his fight against Hanzou, Nagato used the technique for around 5-10 seconds and it put him in a life threatening state. With the use of bunshin and crow feints, Itachi can evade the technique for enough time as the Soul Dragons are
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: meaning that either Nagato will die from his life force and chakra being totally depleted (causing the gedo to automatically reverse summoned) or He'll be forced to cancel the technique in order to save his life.