Juventus star Douglas Costa has rejected calls he should offer a direct apology to Federico Di Francesco after he was sent off for spitting in the Sassuolo winger's face, claiming "you do not know what he said to me."

Brazilian Costa is facing up to both an expected heavy fine from his club and also a suspension from the Italian Football Federation following the incident late on during Sunday's Serie A match.

The flash point came during stoppage time at the end of the game as Juventus saw out a 2-1 victory, with Cristiano Ronaldo scoring twice.

The player's actions were branded as unacceptable by Juventus head coach Massimiliano Allegri, with the club expected to issue internal sanctions.

Costa later offered acknowledgement of his "bad mistake" in a post on Instagram.

However, while his statement apologised to "all Juventus fans for this misleading reaction" as well as his team-mates, there was no reference to Di Francesco himself.

On Monday, the Juventus player responded to one of the several thousands of social media comments, which questioned why he had not issued a direct apology to his opponent.

Costa wrote on Instagram: "You don't know what he said to me. But no big deal... I say sorry to all those who I have to say it to, because I did wrong."

The Italian football authorities are expected to review television footage of the match, including previous incidents between the players, before taking disciplinary action, which is expected to be confirmed on Tuesday.