Zinedine Zidane's agent has said that Marco Materazzi provoked the France captain into head-butting him during Sunday's World Cup final.
Alain Migliaccio insists that Zidane's action was caused by a "very serious" comment that the Italian defender made.
The 34-year-old, who was making his final appearance before retiring from the game, butted Materazzi in the chest during extra-time as Italy went on to clinch the trophy after a penalty shootout.
"He told me Materazzi said something very serious to him but he wouldn't tell me what," Migliaccio told BBC Radio Five Live.
"Zinedine didn't want to talk about it but he will talk about it in the next couple of days.
"He is a man who normally lets things wash over him but on Sunday night something exploded inside him.
"He was very disappointed and sad. He didn't want it to end this way."
According to reports in French newspaper L'Equipe, Materazzi goaded the Algerian-French Zidane by calling him "a terrorist".