However, Ronaldo is seemingly in line to feature in the Group D contest against Atleti, an opponent the former Real Madrid star has scored 25 times against in his prolific career.
"Yesterday he did the training sessions with his team-mates," Sarri said. "He seems to be growing [stronger].
"We will evaluate it between today and tomorrow to see if we have solved it, but the fact that yesterday he did all the training with his team-mates is very positive.
"I think and hope there will be no repercussions."
Ronaldo's relationship with Sarri has been under the microscope in recent weeks, mainly due to the coach's decision to haul off his star forward in two straight matches when Juve were chasing a win prior to the international break.
The second of those games, a 1-0 victory over AC Milan, saw Ronaldo head straight down the tunnel and reportedly leave the stadium before the match had finished.
However, Sarri insists all is well between the duo and he has no objection to players showing frustration when being substituted.
"My relationship with Cristiano is good," he added.
"If a player who has won so much is angry about being substituted it means he still has a lot of motivation and this is something positive.
"It is 25 years I have seen players get angry over substitutions."
Sarri, who confirmed Matthijs de Ligt and Federico Bernardeschi will also be evaluated before the game with Atleti, also explained why he does not foresee Ronaldo, Gonzalo Higuain and Paulo Dybala lining up in the same XI any time soon.
"Playing Paulo, Gonzalo and Cristiano all together is difficult because of their characteristics, but all three know how to play really well and are comfortable with each other," he said.
"We have three strong strikers for two places. None of the three can play 65 games as seen in the early part of the season. Everyone will find a place."
Juve have already qualified for the knockout phase of the Champions League but know a win over Atleti will secure top spot in Group D.
"Right now I'm seeing the team play excellently in flashes and I would like to see some more continuity in certain aspects, but we must take into account the characteristics of the players," Sarri said.
"We certainly have room for improvement. Against Atleti we can't worry about what they are going to do.
"They are a difficult team to face but we must think about how important first place in the group is."