The Portugese star was rested in the 3-1 victory away to Atalanta last weekend, but return in Tuesday's victory over Atletico Madrid in the UEFA Champions League.
Sarri revealed Ronaldo has trained with the team for Sunday's clash with Sassuolo, although he did do some training on his own.
"Cristiano is an immense resource. He has stamina, but perhaps lacks a little in sharpness right now, which is only to be expected," replied Sarri in his press conference.
"We have three forwards of enormous potential, so we always expect a great deal from them. Cristiano trained well, partly with the team and partly in a separate routine, but he is available. All great strikers get irritable if they don't score goals and I think it is a healthy attitude.
"Look, clearly Ronaldo is not a player like all the others, no matter what you're supposed to say.
"Not all players are the same. If someone were to not accept that situation, it'd be a problem for them and not for the team, but I see no such issues. Everyone is crystal clear."