Board Thread:Versus Debates/@comment-26958911-20151010214426/@comment-26537507-20151022221440

I'm not sure if Itachi knows enough about Sage mode to do that. With Sasuke vs Danzo there was an obvious correlation between the amount of eyes left and how long Danzo could maintain Izanagi for. I don't think that the nature energy balance necessary for Sage mode is common knowledge since so few people had actually achieved Sage mode.