Ravanelli, the Marseilles and former Middlesbrough striker, is suffering from bronchial pneumonia and has been replaced by Parma's Enrico Chiesa, who has been in France with the party as cover for Del Piero.
Ravanelli fell ill on Tuesday with a persistent sore throat and a high temperature. He has been told to rest completely for five to six days by the squad's medical team. Italy's coach, Cesare Maldini, said: "It's a great shame for Fabrizio. He's worked hard for four years to get to this World Cup. But we couldn't afford to wait."
Ravanelli's illness comes a week after his three-year old son, Luca, was rushed to hospital in Italy with a virus which caused a fever and vomiting. "The two illnesses aren't related," Stefano Balducci, the Italians' press officer, said.
Without Ravanelli and Del Piero, Roberto Baggio and Christian Vieri will be playing together in a competitive match for the first time in attack. At the back, Maldini, has handed Alessandro Nesta the job of marking Chile's Italian-based striker Ivan Zamorano.
In the other game in Group B, Cameroon take on Austria in Toulouse. The African side's coach, Claude Le Roy, knows his young side must break through an organised defence as they did most famously in 1990, when they beat the holders Argentina in the opening game and went on to reach the last eight.
"We know it will be very difficult. Italy are above us, Chile are a little bit above, and therefore we will have to fight against Austria," Le Roy said.
The veteran Austrians, who have not enjoyed the best of warm-up campaigns, hope that their experience will tell against their younger opponents, who have seven players aged 23 or under in the squad, including the 17- year-old Samuel Eto'o, the youngest player at the tournament. In contrast, 11 of the Austrian 22 are over 30.
"It's very important to get three points in the first game. Otherwise it's going to be difficult," the Austrian central defender Anton Pfeffer said.
Although Cameroon have secured some decent wins recently, including a 2-1 friendly victory in Denmark, they still lack a regular goalscorer. The veteran striker Francois Omam-Biyik, the scorer of the goal that beat Argentina in 1990, hit both goals in Copenhagen but is unlikely to last the full 90 minutes.
Austria's coach, Herbert Prohaska, said: "Cameroon have done well in their recent games, we've done less well. We have to change that. I think they have a very good defence, but we'll try to get an early goal and then we'll have more self-confidence."