Allegri, Chiellini defend Costa over spitting ban
Costa will serve a suspension for spitting in the face of Sassuolo's Federico Di Francesco on Sunday, also headbutting and elbowing the attacker during the clash.
Allegri previously suggested Costa was provoked, while Di Francesco furiously denied reports he racially abused the Brazil international.
And Allegri indicated he wants to move on from the incident, with Costa still in his plans for Wednesday's Champions League opener against Valencia.
"The episode on Sunday surprised everyone," Allegri told a news conference. "And in my opinion, Costa apologised and will pay with the suspension.
"He will have the opportunity to show that this is an isolated gesture, a bad example for children.
"[On Monday] he had a good workout and again this morning [Tuesday]. He had a moment of madness - that should not happen.
"The club will not appeal for Costa. The boy suffered a shock because it is something outside of the behaviour he has always shown on the field. Usually when he passes by a fly he dodges it.
"[Wednesday's] choice on Costa will be exclusively technical."
@chiellini: "I still talk often to @gianluigibuffon and I'd love to meet him again on the pitch in the @ChampionsLeague!"#UCL #VCFJuve
— JuventusFC (@juventusfcen) September 18, 2018
Juventus captain Chiellini defended his team-mate Costa, saying: "The lads are behind Costa. What happened on Sunday was very uncharacteristic of him.
"He's said sorry, he'll pay the price, but at the same time he should not be crucified.
"He'll help us in the Champions League and Serie A from late October."
@OfficialAllegri: "Tomorrow I can confirm @chiellini and @bonucci_leo19 in defence, one from @MarioMandzukic9 or @PauDybala_JR in attack, while down the flanks I have Cancelo, Alex Sandro and @Cuadrado to pick from."#UCL #VCFJuve
— JuventusFC (@juventusfcen) September 18, 2018
Cristiano Ronaldo is in line to make his first Champions League appearance for Juve after joining from Real Madrid, where he won the tournament in each of the last three seasons.
Allegri said: "We have Cristiano, one of the best two players on the planet in recent years, but let's not forget that we've reached two of the last four Champions League finals. We're growing in confidence and we know that we're in with a shout.
"Our objective is to consistently be among the top four Champions League clubs. Are we favourites this year? Let's start winning in difficult places like this one and see how we build from there."