Juventus have been warned they face tough sanctions if their fans target Manchester City's Mario Balotelli with racist abuse once again.
City's new signing suffered abuse from Juve fans while playing for former club Inter Milan.
The abuse surfaced after the striker, who is of Ghanaian descent, was selected for the national team and Juve were punished by being ordered to play a match behind closed doors.
City will face the Italian side in Europa League Group A and Uefa have warned they want no repeat.
Uefa general secretary Gianni Infantino said: "They know that our disciplinary bodies are watching. There will be sanctions if racism is used.
"Uefa have a zero tolerance to racism. No one is getting away with anything do to with racism."
Juventus chief executive Jean-Claude Blanc said Balotelli's return offers fans the chance to prove they had changed.
Blanc said: "This will be the chance for the tifosi to demonstrate that the standard has been raised - hopefully fans will behave the way they should be behaving and supporting the team and only this.
"Supporting your team is to support your team, and not to make remarks of a racist nature toward other players. We will be extremely demanding and intransigent about this."
Manchester City's football administrator Brian Marwood said the club did not anticipate any targeting of Balotelli.
He said: "I'm sure Mario, like all of our players, will be relishing the opportunity. He's a young man with an incredibly bright future ahead of him and we will give him every support and help that he needs.
"We will leave it to the authorities to deal with anything that happens but we are not anticipating any issue.
"Juventus have a great history and we are very proud to be playing against them. It's quite daunting to think we will be facing one of the greatest teams ever to have played European football but we are looking forward to the challenge.
"There's a lot of big teams in this competition and that adds to the excitement of playing in Europe. We had a good campaign last time and got to the quarter-finals and hopefully we can go further.
"Everyone knows we have invested in the team and have bought a lot of top-quality players and it's fixtures like the Juventus game that we want to be playing on a regular basis."