Analysis: Crunch Time for Ferrari

Although Rubens Barrichello declared himself delighted with the pace of the car during his first outing at Mugello, it has since emerged that his day's running was curtailed by a reliability problem - possibly in the engine - on his final lap of the day.

"I felt something wasn't right and immediately turned off the engine," said the Brazilian after the test.

The doubts about the car's reliability will be a major headache for the team, who are well aware that they must turnaround their form quickly if they are not to lose too much ground to current Championship leaders Renault. That is why Michael Schumacher will he hoping for his first run in the new car today is as trouble-free as possible.

Ferrari's technical chiefs have made no secret of the fact that they believe the F2005 to be up to one second per lap quicker than the F2004M - but such speed will be of no use to the team in Championship terms if the car is not reliable enough to finish races.

Technical director Ross Brawn hinted before this week's test that reliability was the main issue the team were worried about with the F2005.

"Some cooling on the car is not adequate, not radiators but other components - the electronic control box is overheating at the moment and we've got a new duct going on the car next week," he said.

"Now, normally you'd have a month or two to sort those things out, so we've got to hope it all lines up. The indications are that Bahrain's a bit easier on the tyres and the temperatures are a bit lower, which is one of the reasons we want to take the new car."

The fact that engines have to last for two race weekends now, and the power-unit on the F2004M is not interchangeable with that of the F20005, means that if the team do not bring the car to Bahrain then they will be stuck with it for the following San Marino Grand Prix.

The complexity of the engine decision also means that Ferrari's engine chief Paolo Martinelli needs as much early warning as possible to be told which version he needs to get ready for Bahrain. That is why the team have set a deadline of tomorrow at the latest, and ideally this evening, to make a firm decision on whether they will take the F2005.

Brawn has made it clear, however, that the team have no regrets yet about their decision to start the season with a modified version of last year's F2004 - although his opinion may change if the F2005 is not the big step-forward that he hopes.

"There were certain technical steps we want to make with the new car which we couldn't do unless we took the extra time," he told Motorsport News on Wednesday. "When the regulations became clear our transmission and engine package was not very good for them because, once you constrain the diffuser on the outside, the central part of the diffuser becomes much more important.

"So you have to expand the inside of the diffuser and then look at your engine and gearbox in a more extreme way. We decided we didn't have the right package, so we had to start again with the transmission.

"Whether it was the right decision, we can judge at the end of the year."