Mexes was sent off after receiving a second yellow card at the weekend for an unrelated incident, with the Italian football federation deciding that the French international's behaviour warranted an additional suspension.
Having reviewed video evidence of the incident, the Federazione Italiana Giuoco Calcio (F.I.G.C.) decided to expand upon the automatic one-game suspension for receiving two yellow cards in a match by banning the defender for three additional games.
Following Juventus' 3-2 win over Milan, in which Chiellini scored the winner, the Italian central defender called for his aggressor to be severely punished, via Football Italia.
Some people are repeat offenders. Toughness and determination in football should be praised, because you have a hard tackle and shake hands, but this is not football.
This sort of thing needs to be punished heavily, because it is not fair play and it is not football. I’ve had some tough tackles in my time, but I don’t recall ever doing that.
The next Milan game that Mexes will be available for is their away trip to Chievo on November 10.
Meanwhile, Massimiliano Allegri will be without the defender for the club's crunch matches against Lazio and Fiorentina, as well as their potentially tricky encounters with Udinese and Parma later in October.
The loss of Mexes will be a major blow for the Rossoneri, who have so far conceded 13 goals in seven games in Serie A this season.
To make matters worse, Milan's next home game against Udinese at the San Siro will have to be played behind closed doors due to another ruling by the F.I.G.C. on the weekend's events.
The ruling body found the club's fans to be guilty of singing insulting chants aimed to insult Juventus fans based on "territorial discrimination," per Football Italia. The club have also been hit with a €50,000 fine for not controlling their supporters.