Ferrari team principal Maurizio Arrivabene said there are "encouraging signs" that his team have made real progress with their 2015 car, but also cautioned that their rivals were masking their true pace.

Ferrari finished quickest in three of the first four days of pre-season testing at Jerez, with Kimi Raikkonen and Sebastian Vettel emerging with the fastest two times overall. And while that dynamic gave him cause for optimism, Arrivabene said the biggest positive to draw was the growing spirit within the team.

"If one makes a comparison to last year, these past few days of testing have produced encouraging signs," he reflected.

"The team has worked well, both at home and at the track and our drivers did a great job, providing the engineers with valuable feedback. But above all, I am pleased that the group has rediscovered its motivation and team spirit.

"In terms of performance, I don't think our competitors - one in particular - have shown their true potential over these past days. I think we will only discover the truth about them and about ourselves at the last Barcelona test session."

Ferrari technical director James Allison, who said in January that there was a wide scope in which the team could improve, added: "When you bring a new car to the track, you're always excited and worried and that is mixed with a profound hope that all the hard work of so many people will be rewarded with performance.

"We leave this test without having all our expectations met, simply because we would have liked to have done even more mileage and because you always want to be faster. However, having said that, given how it went, overall we can be pleased, because we have had a solid start.

"Now, we are keen to push on with the development work in Barcelona, so as to be ready for the first race in Melbourne."

Pre-season testing resumes in two weeks' time at Barcelona on February 19-22