Mercedes' Formula 1 rivals believe its factory team is "hiding" its performance so far during the first Bahrain pre-season test.
Mercedes - on the strength of its new power unit - has been the consensus pick as favourite for this new era of F1 through the off-season and the behind-closed-doors test at Barcelona.
But team principal Toto Wolff rang the alarm bell on the opening day of public running in Bahrain, claiming that Red Bull had a decisive energy deployment advantage from its bespoke, Ford-aided power unit.
Wolff's claim, which came against the backdrop of the ongoing political wrangling over a compression ratio trick Mercedes is thought to be making the most of, was backed up by driver George Russell on the third and final day of the test.
"I do think this test has been a bit of a reality check for all of us," Russell insisted. "Firstly, a huge amount of chat regarded Mercedes and our power unit in the winter, all of which is speculation, because nobody knows anything at that point.
"The truth is, Red Bull in Barcelona, day one, hit the ground running and were well ahead of all of their competitors - so ourselves, Ferrari, and the others. Day one here in Bahrain again they sort of knocked it out the park.
"At the moment, they're very much the team to beat."
As is the norm, however, these suggestions from Mercedes have been rebuffed very strongly by direct rivals.
"I think everybody is trying to throw the ball to the other guy!" said Ferrari driver Charles Leclerc.
"It's normal at this point of the season. Also because it's so difficult to understand. It was difficult with the previous generation of cars but now with the hybrid and especially the electrical engine being so much more powerful, there are so many small tweaks that you can do, and you can hide the real potential of the car in many-many different ways now.
"I think Red Bull have shown very impressive things, power unit-wise, since the start of the tests, especially here. Mercedes are showing... some very impressive things as well, sometimes, but I would say they are hiding a lot more. And, yeah, I would expect them two especially to be a bit ahead of us.
"Then [Mercedes-engined] McLaren is a little bit more difficult to understand. But from where I stand now, it's Red Bull and Mercedes in front, and then us, but it doesn't seem to be too much of a gap for now."
"What is mega good is that nobody is speaking about us!" laughed Ferrari team boss Fred Vasseur. "I like this situation, we can be focused on ourselves.
"Still nobody knows. Nobody knows the Mercedes, if they push the engine or not - looks like not! And nobody knows over a stint if you have 20 kilos [of fuel] 40 kilos or 60 kilos. And this is much more than the difference between the cars."
Red Bull driver Max Verstappen was a lot more flat out in his insistence that Mercedes was obscuring its potential.
Verstappen indicated to Dutch media that he believed Mercedes was trying to deflect attention from itself amid the ongoing compression ratio deliberations.
"I can tell you one thing - just wait until Melbourne and watch how much more power they will suddenly have. I already know that," he said.
"Just wait until Melbourne and see how fast they suddenly go on the straight."
Russell's argument for why Red Bull is the team to look at for the Australian Grand Prix instead is that it has looked the most ready when hitting the track at the beginning of the two tests.
"It's quite straightforward when you have three days of testing in the same location to make those improvements," said Russell.
"But when you get to Melbourne, and you've got three practice sessions, you've got three hours of practice before qualifying - based on what we've seen in Barcelona and Bahrain, Red Bull are going to be ahead. So yeah, we've got work to do."
