Board Thread:Theories and Speculation/@comment-36019309-20190114073523/@comment-734582-20190114190155

MadEyes008 wrote: If Itachi’s Tsukuyomi succeeded than it would have ruined everything and the only way he could make sure Sasuke wouldn’t lose is by holding back. This is why Itachi used it several times on Sasuke, so he could get used to it and break out. It's made fairly clear that Sasuke is capable of breaking out, Itachi, Zetsu and the databooks point to this.

Itachi was holding back by not going for every obvious opening to murder his brother. The very opening of the fight has Itachi resoundly win the Genjutsu battle. Yet he doesn't move and just sits and gloats. But the jutsu he used were full strength. Itachi nearly breaks his cover by failing to dodge the Shuriken, indicating he was fully serious.