Barrichello joined the Renault drivers on the Melbourne podium

Renault design boss Bob Bell said: "We are not under any illusions - Ferrari are probably still the strongest team.

"Don't forget they ran with a modified version of last year's car; there is still the new car to come.

"They will be very strong all season, and I expect McLaren and even Williams to be up there too."

Bell, Renault's technical director, said he was pleased with how his car and team had performed in Australia, where Fernando Alonso finished third to join team-mate Fisichella on the podium.

But he said that the next race in Malaysia would present challenges they had not yet faced in 2005.

"It is a race full of unknowns," Bell said.

"First of all, we will have to re-use the engine - which is something that we have simulated, but never had to do before in race conditions.

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"Indeed, the weather conditions in Melbourne were not at all extreme - it was more like the end of winter testing than a Grand Prix.

"Malaysia, for sure, will be extremely hot and humid as well. That will make it a completely different challenge for the tyres, and until we get there, we do not know how the car will cope with that."