Samuel Eto'o risks a long ban after the Inter striker was caught on camera head-butting Cesar in a Zinedine Zidane-Marco Materazzi style.
The off the ball incident occurred 38 minutes into today's Serie A match against Chievo.
The two players had argued a few moments earlier and Eto'o opted to take 'revenge' by running towards him to head-butt Cesar in the chest.
The referee, assistants and fourth official at the Stadio Bentegodi did not see the incident, but it was caught on camera.
This means Eto'o should prepare for video evidence to be used against him and potentially a lengthy ban.
It was very similar to the infamous Zidane head-butt on Materazzi in the 2006 World Cup Final, which saw the France legend sent off in his last ever game.
At half-time, Inter are trailing 1-0 to Chievo thanks to a Sergio Pellissier header.