"It has been my ever best moment," he says, his wide brown eyes lighting up again at the memory, his improving English seeking to do justice to the sequence of events as you prod him to provide you with the details. "It is going to remain always in my mind. I think it's destiny," he adds. "I couldn't even think about something like that."
Cup finals are mostly about early sparring until nerves settle and range is found. Di Matteo seemed to have none and no trouble with target and distance. Picking up the ball in his own half, some 70 yards from the Middlesbrough goal, he advanced hopefully, the game still waking up and a yawning gap appearing ahead.
"I have space in front of me and I started to run," he recalls. "Then I saw Sparky [Mark Hughes] in front of me. He made a little run on the right side and I thought `Ah well, let me just try something because the game has just started and it doesn't matter anyway'.
"Someone was on my left. It was Emerson but he couldn't reach me." You interrupt to suggest that the trying, sometimes non-trying, Brazilian must have been tired and Di Matteo again flashes that expansive smile. As then, he is in full flow and will not be put off his stride.
"The defender went with Sparky. The other defender came just a little bit up but it was quite far, so maybe they didn't expect me to shoot." From more than 30 yards he did and the ball flew through Ben Roberts's flailing arms, fizzed off the underside of the bar and into the net.
"Yeah, yeah, yeah," he replies when you ask him if he knew the ball's fate instantly. "I felt it straight away and when I saw the ball it was incredible." How often do you hit a ball like that? "Not very often. If you see the pictures, I hit the ball at the front of my foot. Usually you shoot with the whole foot but because it came from the front of my foot, it went up and then down over the goalkeeper. It had to happen. It was my day."
It being the Cup with its glorious capacity for human interest, up in Wembley's stands his blind sister Concetta was being told that the mayhem going on around her had been caused by her family. It being the Cup, too, with its capacity to deflate, it has been decreed that Chelsea begin their defence this afternoon against Manchester United, the only consolation being the advantage of Stamford Bridge, in a match that would have graced the final. "To be honest, I would have liked another team," he admits.
It is a year ago this month since Di Matteo became aware of the importance to this country of its main cup competition. After a 3-0 win over West Bromwich Albion came that come-from-behind 4-2 win over Liverpool which set Chelsea believing anything was possible. "I think it is almost more important than the league," he says. "People go mad for the Cup. At the training ground before every Cup game a lot of people come, but for the league games just a few. In Italy it is not that important until the semi- final or final."
Di Matteo's time in England had not begun especially well after his move from Lazio. More attention was paid to his fellow Italian Gianluca Vialli, though back home they were more concerned at losing a player, then 27, at his peak. Di Matteo struggled to impress. "I had problems with my back and couldn't do pre-season," he explains. "I was having injections to play. Also, I had to learn to protect myself. It is a bit harder here, when you get tackled or challenged you can get injured."
But what of Italian defenders? "Yes, they are very tough but the referees there whistle very quick. In England, also you play much quicker. In Italy, the way they play is good for them, here it is right for the people here. I have no problem with that. I like it, this action." In fact, one thing that surprises you about Di Matteo close up is a slightness of frame that belies his physical presence on the field.
Gullit rested Di Matteo in November of 1996 but after that, and with the arrival of Gianfranco Zola as an outlet for his forward passing, his form improved to the extent that it was easy to see why Chelsea had paid almost pounds 5m for him. His energy, sharp tackling and quick passing - which England can be grateful they did not have to face in Rome last October when he was suspended - make him a model modern midfield player, which has little to do with the brown Versace jeans and yellow Ralph Lauren shirt he is wearing.
Di Matteo cites Gullit as a big reason for him signing, as well as having enjoyed London as the latest stage of his enlightening journey. He shrugs off the racism he encountered as a child growing up as an Italian in Switzerland. "I am a very lucky boy," he says of his career path.
"Ruud is very interesting," he adds. "He has got a big charisma. You respect him and you believe him because he is a great figure. We have got our tactics but he lets players have the freedom at certain moments to decide what they want to do. It is a pity he doesn't play any more because he is a great player."
Is there not, though, a suggestion that he will play today? "If the manager picks him," says Di Matteo, revealing a feeling for the nuances of English humour that he picks up by watching movies on television and using the sub-titles for the deaf to improve his understanding.
Despite the difficulty of today's draw, the game could, perversely, come as respite for Chelsea, after taking only one point from the Christmas games against Wimbledon and Southampton. The opposite side of their capacity to lose to the lower teams is an ability to beat the best. "We have never lost to Manchester United since I have been here," says Di Matteo, "and we still think we can challenge them for the league. There are so many games yet. I know no team has won losing more than six games but we will fight to the end."
He reluctantly concedes that what sets United apart from the rest of the Premiership is the quality and depth of their squad. "The main problem for us at the moment is that we have got a few suspensions and injuries and you can't just replace important players like Dennis Wise, Gustavo Poyet and Franck Leboeuf. When everybody is fit we have a strong team."
What of the reputation that he must have heard about, of Chelsea being very pretty but with a soft centre? "I think you get stronger with success," he says. "Because then you believe in yourself more and more and you get mentally stronger. We are third in the league, in the Cup-Winners' Cup and Coca-Cola Cup quarter-finals so I think we have improved. But still the most important thing to win a trophy is to have quality players."
And charm too - but not of the sort Di Matteo possesses in abundance. Concetta, his lucky charm, has been in London for the Christmas break and will be at the match. "I told you already, I am a very lucky boy," warns the brown-eyed boy.Reuse content