"Unfortunately it went badly," said Matrix after the result sliced Inter's lead to just one point from Roma. "I think last season the order of penalty-takers was the same, but at the time and today I felt like taking it. Unfortunately I made a mistake.
"Perhaps with hindsight I should have left it to Cruz. I apologised to him afterwards."
Julio Cruz was furious at the decision and had to be held back by teammates so that Materazzi could take the kick.
He added: "This is part of the sport and the sense of disappointment it can give you, so I can't complain."
