Mercedes has elected against running the softest two tyre compounds for this week's final pre-season Formula 1 test, meaning the full potential of its new W07 will not be known until Melbourne.
Instead, with the high demands of the Barcelona track only suitable for harder rubber, Mercedes is to stick to running just the soft and medium compounds.
Speaking to select media, including Motorsport.com, on the first day of this week's Barcelona test, Mercedes motorsport boss Toto Wolff said: "Our work programme has been defined by time and does not allow us to use compounds that are not usually used at this track.
"Nico [Rosberg] tried the soft for the first time this morning with good results, but mainly we will continue to run on the medium."
The decision not to run the softest tyres shows how much confidence the team has in its preparations for the new campaign.
Mercedes could theoretically unleash an extra 1.2 seconds from its car for a lap of Barcelona if it ran the ultrasoft.
The ultrasoft is understood to be around 0.6 seconds quicker than the supersoft, which is 0.6 seconds faster than the soft.
Wolff said he was delighted with how Mercedes' early preparation had gone, as he hailed it the best pre-season his outfit had had.
"If we consider the testing preparations of 2014 to 2016, then this year they are undoubtedly the best," he said.
"In part I think it is due to the stable regulations that has made us grow season after season, but also there is of course an excellent job done by the whole team.
Rosberg, meanwhile, said after the end of the first day of work that Ferrari was close to Mercedes.
"It's close out there between the two teams I think - and maybe some other team might be there as well.
"It's difficult to know where [the teams are] exactly, but [Ferrari] have done a great job so we really need to give everything because they're very close and a big threat. But of course we're confident and we're ready for the battle."
Interview by Roberto Chinchero