Ronaldo has been in spectacular form in 2020 and has scored 11 goals in his last seven matches across all competitions, while he is also on a Juve record run after netting in 10 consecutive Serie A games.
The Portugal international's fitness was brought up by reporters ahead of Thursday's Coppa Italia semi-final first leg away to Milan, but Sarri insisted the forward was feeling strong a fortnight before their continental tie against Lyon begins.
"We will see," Sarri said about the prospect of resting Ronaldo.
"I have spoken with him and he told me he is feeling well right now. We will evaluate him on a game by game basis."
Sarri also provided an update on Giorgio Chiellini, who has not played since August having had surgery in September on a ruptured cruciate ligament.
The Juve boss said last week that the defender was closing in on a return and was positive again after Chiellini had taken part in a shortened friendly match involving Juventus' youth players and local team Chisola.
"Chiellini's road to recovery looks good," said Sarri. "He needs to do a few more tests like he did this morning."
Opponents Milan come into the game on the back of a morale-denting 4-2 derby loss to Inter, but Sarri is taking nothing for granted at San Siro.
"Milan have improved a lot in this period," said the former Chelsea boss, whose side are hoping to bounce back from a surprise 2-1 away Serie A loss to Hellas Verona.
"They come into the game off the back of the derby in which they played well. It will be a difficult game.
"My team is training well, with intensity and application. The standard is very high."