The striker knows the same nightmare situation could arise at Euro 2012.
By surrendering the lead in a 1-1 draw with Croatia on Thursday, Italy is third with two points in Group C with one match remaining and no longer has its destiny in its own hands.
If Spain and Croatia — who both have four points — draw with a score of 2-2 or higher on Monday, Italy will be eliminated even if the team beats Ireland in the final round of group matches.
The scenario is similar to 2004 — the Azzurri beat Bulgaria in their third group match but were eliminated after Sweden and Denmark drew 2-2.
"There are going to be two teams of different levels facing each other and Spain, which is the favourite, has players with a pedigree that won't allow them to be unsportsmanlike," said Italy goalkeeper Gianluigi Buffon, who had the job of consoling Cassano that night in Guimaraes after his teammate's injury-time winner.
Italy was coached by Giovanni Trapattoni in 2004 and, as fate would have it, he is now in charge of an already-eliminated Ireland team that is looking to salvage some pride in its last game after two straight losses.
Italian media are speculating about a plot between Spain and Croatia to eliminate the Azzurri, but current Italy coach Cesare Prandelli wouldn't be drawn into the debate.
"This is a controversy I have a hard time understanding," he said. "Over the past 10 years, Spain has enthused the entire world and everyone wants to copy them and you want me to think this squad is contemplating a (plot against Italy)? Whoever does that has problems. We don't need to look for excuses."
The Italians are not without hope.
If they win and the other match doesn't end in a draw, they will advance as the second-place team in the group. Or if Italy wins and Spain-Croatia finishes 0-0, the Azzurri will win the group.
Alternatively, if Italy wins and Spain-Croatia finishes 1-1, the Azzurri will advance if they beat Ireland by at least three goals or by scores of 3-1 or 4-2 — based on a better UEFA ranking.
"We have the duty to believe until the end," Prandelli said. "We shouldn't give in to this culture of skepticism. That's what I told the squad. We've got to think exclusively about Ireland."
Italy could have avoided these last-match calculations, however, if it hadn't sat back after going in front against Croatia thanks to Andrea Pirlo's free kick at the end of the first half.
After having six shots on goal in the first half, they had only one in the second.
"The first half was how we should always play, and the second was how we should never play," Italy midfielder Claudio Marchisio said. "We've got to figure out what happened. Our strikers weren't able to press forward anymore."
That wasn't the fault of Mario Balotelli or Cassano, Marchisio said.
"We're all at fault, and the same goes for the match against Spain," he added, in reference to the 1-1 draw in Italy's opening game. "This isn't a tournament where you can draw, you've got to close out matches here and win them."
Marchisio disagreed with the analysis of Prandelli, who cited a drop in energy and fitness after an hour.
"I don't think so," Marchisio said. "I think we let up mentally."