"The day Schumacher gets back, it will be to help Ferrari, there's no doubt about it," Luca di Montezemolo, the Ferrari chairman, said. "What we care about is Ferrari's victory."
The German, who broke his right leg in two places in a head-on crash into a tyre wall at Silverstone last month, might be back at the Monza Grand Prix on 12 September.
"At that point he will have no chance to contend for the title," Montezemolo said. These were the first such remarks from the Italian team since the accident that injured Schumacher, twice the world champion and considered by most observers to be the best driver in the world.
Irvine, initially the No 2 driver on the team but now the main man, won the last two races and now leads the defending champion, Mika Hakkinen, in the standings. The Ulsterman has let Schumacher pass on a number of occasions in past seasons.
"Drivers must follow directives," said Montezemolo. "Schumacher has said it and will do it. He'll be at Ferrari's service."
In an interview on German television after his accident, Schumacher had said he could accept driving behind Irvine to help Ferrari capture their first drivers' title in 20 years.
In the CART FedEx Championship in the United States, Scotland's Dario Franchitti took advantage when Colombia's Juan Montoya made a late pit stop on Sunday in a mistake-filled Grand Prix of Detroit.
Franchitti coasted to a victory - his second of the season - which him into first place in the series standings with 136 points, five ahead of Montoya, the rookie who had led the championship by 13 points going into the race.
Franchitti, who won on a similar temporary street circuit in Toronto on 18 July, has finished no worse than third in seven of his past nine starts on such courses.
Numerous wrecks caused 23 laps of the 75-lap race to be run under the caution flag. As a result of the delays, race officials decided to limit the competition to two hours, so only 71 laps were completed.
Nine of the 26 cars that started failed to finish. Canada's Patrick Carpentier needed hospital treatment for neck and back injuries after colliding with Brazil's Mauricio Gugelmin in the worst crash.