The 34-year-old was replaced by Paulo Dybala in the 55th minute during Juve's Serie A clash with AC Milan and immediately made his way up the tunnel after coming from the pitch, goal.com reported.
Reports in Italy also suggested Ronaldo left the stadium three minutes prior to the end of the match – which Dybala ultimately decided with a 77th-minute strike.
Ronaldo was also replaced midweek in the Champions League with Sarri revealing the full extent of his star's fitness issues and stressing that he's fine with the attacker being upset about the situation.
“We must thank Ronaldo, because he made a sacrifice to be there at all tonight in a difficult situation," Sarri told Sky Sport Italia post-match.
"He did everything possible to play, but I saw he was not well and thought it best to take him off. It’s only natural a player is going to be irritated to leave the pitch, especially when he worked so hard to be there.
"Over the last month, he has had this little knee problem, he had a knock in training and it hurt the collateral ligament. When he trains at high intensity or plays, it unbalances him, so he ends up overcompensating and it damages the calf and thigh muscles.
“It is affecting his performances and he is not at his best at the moment. All players who are trying to give their best will have at least five minutes of being annoyed when they are substituted, but a coach would in general be much more worried if he didn’t seem upset.”
Juventus ultimately made do without Ronaldo as Dybala once again found the back of the net against AC Milan to seal a 1-0 win for Sarri's side.
The Old Lady is now one point clear at the top of Serie A with Sarri impressed with his team's desire, if not the performance on Sunday.
“I liked the spirit of the team, but we have to improve immensely in terms of quality, as we made too many mistakes, gave the ball away cheaply and opened up spaces for Milan. The hunger and determination to win is what kept us going,” Sarri said.