Ferrari have been forced to make a major redesign of their car as a result of flaws discovered since it ran in pre-season testing in February.
Team boss Mattia Binotto said work on understanding why the car was off the pace led to a "significant change of direction in terms of development".
The result is the car will run in pre-season specification at this weekend's delayed season-opening race in Austria.
The upgrade is due to make its debut at the Hungarian Grand Prix on 17-19 July.
Binotto said the team had been forced to revise their approach to the car's aerodynamics following their investigation into its performance shortfall.
"We had to understand why we did not see the results we had expected on track and how much to recalibrate the whole programme as a result," Binotto said.
"It would have been counterproductive to continue in the direction we had planned, knowing that we would not have reached our goals.
"Therefore we decided to come up with a new programme that looked at the whole car, knowing that not all of it would be ready for the first race.
"Our aim is to introduce the updates at the third race at the Hungaroring.
"Apart from that, over and above the actual development of the car itself, these past few weeks we have worked a lot on analysing its behaviour, with simulation work and with the help of our drivers and I think that will prove its worth in Austria.
"We know that, at the moment, we don't have the fastest package. We knew it before heading for Melbourne and that hasn't changed.
"Having said that, the Spielberg circuit has different characteristics to Montmelo (in Spain, where testing was held) and the temperatures will be well above those of February.
"In Austria, we must try and make the most of every opportunity and then in Hungary, with the new development step we are working on, we will be able to see where we are really compared to the others, while having to take into account the developments our competitors themselves will have brought along."
The outcome is that Ferrari are unlikely to be in the fight for victory at the first two races at the Red Bull Ring this weekend and next.
Not only were they already off the pace of Mercedes and Red Bull, but both their rivals have upgrades on their cars which will make them faster.
Mercedes have delivered a significant aerodynamic upgrade to their car as Lewis Hamilton embarks on his bid to win a record-equalling seventh world title.
And Red Bull have an improved Honda engine to add to their own aerodynamic progress.
Ferrari driver Sebastian Vettel, who starts the season knowing it will be his last with the team, said: "We have to be realistic when it comes to the pecking order seen at the tests, but we are not downhearted."
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