Ronaldo was taken off in the win over AC Milan on Sunday evening before he had words with Sarri and stormed down the tunnel.
Sarri played down the incident and claimed Ronaldo had been struggling with a knee injury, but the Selecao manager claims his top scorer raring to go for the upcoming 2020 European Championship qualifiers.
"If he wasn't fit we wouldn't have called him up. Everyone likes to talk and speculate about Cristiano Ronaldo because he is the best player in the world," Santos said, according to Daily Mail.
"If it was any other player there would be no such fuss. He is fit and he's going to play.
"This conference is not about Cristiano Ronaldo, it's about Portugal and the game with Lithuania."
The European champions will lock horns with Lithuania on Thursday evening, before they travel to Luxembourg three days later.