Toto Wolff has hit back at Dr Helmut Marko's estimation of the 2019 pecking order.
"I don't think anyone can tell if someone is two tenths ahead or two tenths back," Wolff, the Mercedes team boss, told APA news agency.
"That would mean they know how much fuel the others had, and we don't."
He admitted, however, that Ferrari does appear to be leading after the winter tests.
"At the moment it looks like Ferrari is ahead, with not much between Red Bull and Mercedes, but as I said, on Saturday and Sunday we will know a little more," said Wolff.
Mercedes ultimately set a good laptime in Barcelona, but Wolff said that is not enough for the German team to feel confident.
"If you look at the eight days, we did a fast lap on the last day but it wasn't that strong on the race simulations," he said.
In contrast, he says Ferrari "put on the track a car that worked well from day one.
"Sebastian said the car goes where he wants it to go. Our car is not yet optimally balanced," added Wolff.
"We had a problem with the stability in high speed with a bit of understeer, and we had understeer in the low speed, especially the last sector."
However, Wolff said Mercedes is not ruling out its title hopes, even given Ferrari's apparent advantage.
"It's not something that's new to us. First we have to understand the car and then we'll see. But somehow this year we do not feel we are in the favourites role, but catching up is also something we enjoy," he said.body check tags ::