Last season Juventus had Chiellini, Barzagli, Bonucci and Caceres, which are all good enough to start at most teams as main center backs. That is four players without even mentioning lesser players like Peluso or even Marrone. Despite that Marotta still got Ogbonna, which makes 5 players that can be mixed without risk of losing too much quality.
I think that midfielders need a lot more rotation, but we still only got 4 quality players for that position. One option is to place Asamoah as a midfielder, but that does not look likely with Conte. I am sure there will be another midfielder coming and Nainggolan is one of the best options.