Cristiano Ronaldo stormed out of the stadium while Juventus' match against AC Milan was still underway on Sunday but Juventus coach Maurizio Sarri has backed his star player.

After Juventus defeated AC Milan 1-0 at home, Sarri said Ronaldo is "not a problem."

After being substituted for the second consecutive match, Ronaldo was clearly displeased. The move eventually paid off for the Serie A champions as Paulo Dybala, who replaced Ronaldo, scored the winner for Juventus against AC Milan.

When the substitution was signaled at the 55th minute, a furious Ronaldo high-fived Dybala, directed a few words at Sarri before he vanished into the players' tunnel. The Portuguese superstar left the stadium three minutes before the match finished, as reported Sky Sport Italia.

Backing his legendary player, Sarri said, "If it's true that he left before the end it is a problem to be resolved with his teammates."

Sarri, who had already mentioned earlier about Ronaldo's knee issues, repeated himself again.

"He [Cristiano] should be thanked because he made himself available despite not being in the best condition. In the last month, he has had discomfort in his knee and this is a little problem for him. The important thing is that he made himself available. If he gets angry when he comes out this is part of the game. It's only natural a player is going to be irritated about leaving the pitch, especially when he worked so hard to be there," Sarri added.

There was another landmark for Cristiano Ronaldo as he scored for Juventus in their 3-0 defeat of Bayer Leverkusen
Cristiano Ronaldo AFP / Isabella BONOTTO

The Juve boss also explained that it's very normal when a player gets annoyed on being substituted and the concern arises when the player is unaffected by it.

"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," Sarri said.

Ronaldo, who has scored just six goals in 14 appearances this season, has already been substituted as many times this campaign as he was throughout the 2018-19 season.

With 10 wins and two draws from 12 matches, reigning champions Juventus, are on the top of the Serie A table, ahead of Inter Milan and Lazo. However, Juventus are just one point clear of Inter and they need Ronaldo to recover quickly and start playing full 90 minutes to ensure they remain unbeaten in the coming matches.