The Bianconeri have had two games since football returned in Italy, both in the Italian Cup, but both have finished 0-0, with them losing the final on penalties to Napoli on Wednesday.
The disappointing results were compounded with a pair of lacklustre, lackadaisical performances in each game, with Juve lacking an attacking spark in the final third.
Ronaldo was by no means Juventus’ worst performer over the two games, earning a 6.5 rating for his outing against Napoli, but by his own high standards he seemed off the pace, only managing one shot on target.
Sarri believes the Portuguese superstar needs to regain energy and sharpness, as Juventus head into the remainder of their Serie A championship battle.
"He's in the same shape as the others, like Paulo Dybala and Douglas Costa, he is lacking the sharpness to do what works best for him,” he told RAI.
"I didn't say much to the players after the game. I was angry and disappointed just like them, so at these moments it's best to stay silent. We'll talk better tomorrow morning."
The Italian believes his team’s inability to get beyond opposition players one-on-one was a key factor in the defeat.
"We are struggling to get past opposition players when taking men on, we have a team built on individuals who can usually do that very well,” he continued.
“I don’t think we’re lacking determination, because we were totally concentrated for 90 minutes and you can’t do that without determination.
"I think the problem is the characteristics, because these are players accustomed to taking men on and at the moment that’s just not coming off."