He said: "We had to accommodate Hazard's characteristics, as he could change the game.
"But also his presence caused issues in defending that we had to work on."
Sarri also went on to hint that he is about to manage better players at Juve than he did working at Stamford Bridge - especially Cristiano Ronaldo.
He added: "I coached some very strong players, but training him will be yet another step forward.
"I'd like to help him break some new records."