Zinedine Zidane's agent Alain Migliaccio said the French great's headbutt on Marco Materazzi was provoked by something "very grave" which he would reveal all when calmer in one or two days.
Migliaccio said he did not know what Materazzi said but Zidane was definitely upset about everything that happened.
"He was very sad for everything that happened but this is life," Migliaccio said.
"He is a human being not a god. I know Zizou well and even though he hasn't told me exactly what Materazzi said, I know that he was provoked. Materazzi said something very grave to him, I don't know what it was.
"I know Zizou well and he will not reveal what Materazzi said to him but he will in one or two days' time, explain why he had such a reaction. When he is calmer he will speak.
The France captain was shown red card for hitting his head into Materazzi's chest in the first period of extra time of the World Cup final - his last game before retirement, at Berlin's Olympic Stadium.
The Italians went on to win a penalty shootout 5-3 after extra time had ended with the score level at 1-1.
"When I saw him at 2 am he was very sad, he didn't want to end his career like this.
"He was simply very sad. He is a person that doesn't say much but bottles it up and then one day explodes," the agent said.
Meanwhile, FIFA has awarded the 34-year-old France's hero of their 1998 World Cup triumph - the Golden Ball as the player of the tournament following a vote taken before his red card.