Chivu oversaw Inter Milan's home defeat to Udinese on the weekend.
There's since been a backlash against the inexperienced coach and Sacchi told La Gazzetta dello Sport: : "It's inevitable. If you're Inter's coach and you lose at home to Udinese, there can't be any applause.
"Chivu's Inter are halfway there: it's unclear whether they're his team or still (Simone) Inzaghi's. It takes patience.
"I can only suggest one thing to Chivu: do everything you can to get inside his players' heads and convince them to follow the path he has outlined. On Sunday against Udinese, I saw a team that was neither harmonious nor balanced.
"Harmony and balance are the foundation of any great team."
Asked about Napoli, Sacchi added: "They bought players based on the style of play the coach wants to implement. That's the way it is done. The only unknown is the double commitment.
"The squad is deep and can face both the league and the Champions League, but international matches are like leeches: they drain your blood, and you lose the energy both in your legs and in your brain."