Juventus head coach Massimiliano Allegri has condemned Douglas Costa's violent outbursts that led to the Brazilian being sent off in a 2-1 win over Sassuolo.
Costa elbowed, headbutted and spat in the face of Federico Di Francesco in the closing stages of a game in which Cristiano Ronaldo scored twice to give Juventus the lead.
The winger could be slapped with a three-match ban that would include Juventus' clash with Serie A title rivals Napoli on September 29.
Though Allegri felt Costa was provoked into his conduct late on at the Allianz Stadium, he also refused to use it as an excuse for the player’s actions.
"Maybe he was irritated at a foul before," the 51-year-old told Sky Sport Italia .
"But it doesn't matter, because this absolutely must not happen.
"The one thing we must avoid doing is falling for provocation.
“We could have scored a third goal, but instead we started to play as individuals.
This is going to be a huge story in world football. Douglas Costa spits in Federico Di Francesco's mouth during the #Juve and #Sassuolo game. pic.twitter.com/IXyYDClct8 — Eleven Sports (@ElevenSports_UK) 16 de septiembre de 2018
"We tried to dribble past everyone. This wound up the opposition, who then reacted badly and you get to situations like Douglas Costa."
Allegri suggested Ronaldo snatched at a number of chances earlier in the game, but said the Portugal superstar's first goal for the club following his transfer from Real Madrid settled his nerves.
"You just had to see the first three games and how close Ronaldo went to scoring," added Allegri.
"Again today, he was a little too hasty and eager to score, but it bounced off the post and right into his path. That unblocked him.
"Today, even though it was the first time with this system, we did well. Naturally, the full-backs have to give more width.
"Sassuolo fought hard and as they became tired later on, we took full control of the game."
Juventus now turn their attention to the Champions League, which Ronaldo won last season, as they face La Liga outfit in the first game of the group stages.
The Serie A title holders will be looking to make it to a third final in five years, having lost to Barcelona and Real Madrid respectively in 2015 and 2017.