Rossi accepted the decision and apologised to Ljajic, but refused to confirm or deny what was said during his farewell press conference.
However, he has now told La Repubblica newspaper what sparked his totally out of character fury.
"While he was going back to the bench Ljajic applauded and said to me: 'Well done, maestro. Really, you're a phenomenon.'
"I told him he shouldn't dare behave like that and he offended me in Serbian. But I have trained many Serbian players in my career and I understood what he said.
"He told me to 'go back in your mother's ****' and at that point I lost it."
The article also claims Ljajic goaded Rossi during the attack, repeatedly telling him to hit harder "as they're going to kick you out anyway."