He is protecting Kean like he protected Rugani, whowas a very good defender 4 years ago and now he still be a substitute without no possibilities to play. This is the right way to destroy young players, not to protect them.
It would be much better to protect old peoples like Mandzukic and Khedira, that have been soccer players some years ago, but now they are only renters, or to protect himself going in a very long vacation in a very far country, where he can rest without to damage his side.
If Messi or Ronaldo started their career with Allegri, he would probably have "protected" them until today, letting them rotten on the bench for years.