Milan - Cristiano Ronaldo reportedly left the Allianz Stadium before the final whistle of Juventus' 1-0 Serie A win over AC Milan on Sunday after being substituted for the second match in a week.

Paulo Dybala replaced Ronaldo on 55 minutes with the Argentina striker going on to score the winning goal 22 minutes later to keep Juventus top in Serie A ahead of Inter Milan.

Five-time Ballon d'Or winner Ronaldo looked glum as he came off and directed some words at coach Maurizio Sarri before heading to the changing rooms and Sky Sport Italia reported that the 34-year-old had left the stadium three minutes before the match finished.

However Sarri said he did not know whether Ronaldo had left the stadium early.

"Disrespectful to his team-mates? Like I said, I don't know," Sarri said. "If it's true that he left before the end it is a problem to be resolved with his team-mates."

"I have no problem with Cristiano, he should be thanked because he made himself available despite not being in the best condition," said Sarri.

"In the last month he has had discomfort in his knee and this is a little problem for him."

Ronaldo had reacted furiously after been substituted in his team's 2-1 win against Lokomotiv Moscow midweek which saw Juventus advance to the Champions League last 16.

"The important thing is that he made himself available. If he gets angry when he comes out this is part of the game," continued the Juventus coach.

"It's only natural a player is going to be irritated about leaving the pitch, especially when he worked so hard to be there.

"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."