​Former Italian striker Antonio Cassano has warned ​Cristiano Ronaldo that leaving the stadium three minutes before the end of ​Juventus' match against ​AC Milan could see him receiving a ban. 

A furious Ronaldo ​left Allianz Stadium before the end of Juventus' ​1-0 triumph over Milan on Sunday, having been substituted early in the second half, and Cassano believes the Portuguese forward could be banned. 

Talking to Italian television show Tiki-Taka, as per AS, Cassano explained how, as a Roma player, he left a game early and had to return as he could have been banned for missing a drugs test, saying, "Did he leave before the end of the game? You can't do that because there is an anti-doping control. I had to go back to the stadium urgently to avoid a two-year ban."

The Old Lady were level at the time of the forward's substitution, with Paulo Dybala coming on as his replacement. The 34-year-old could not hide his frustration after his evening came to a close with 35 minutes still left to play, but ​Maurizio Sarri's decision proved pivotal as Dybala struck the winner as the game entered the final 15 minutes.

Sky Sports Italia report that the former Real Madrid superstar did not wait for his teammates to return from the field of play. The victory keeps the Bianconeri at the top of the ​Serie A table, a point ahead of ​Inter after collecting ten wins from the first 12 fixtures of the season.

Sarri has since explained the reasoning behind Ronaldo's withdrawal, revealing (as quoted by AS): "He was hit in a training session. He suffered a knee bruise. Maybe the right knee, if I remember correctly. It's not a big issue, no twist, only a bruise at the collateral ligament. When he steps he can't push as usual, but I am not worried about it."

Prior to his substitutions against the Rossoneri and Lokomotiv Moscow, Ronaldo had never been taken off in successive matches for Juventus.

In 2019/20, he has failed to produce the performance levels that helped Real conquer Europe on four separate occasions. The same is true of his first campaign in Turin, when the veteran was just the fourth highest scorer in the league.