The German manufacturer had come into this year hoping that a design revamp would help it close the gap on pacesetter Red Bull.
However, drivers George Russell and Lewis Hamilton have endured a challenging first two races to the campaign with a clear weakness to the car now exposed.
Team principal Toto Wolff says Mercedes does not fully comprehend what is going wrong in high-speed corners, as its real-world performance is not matching what its data suggests.
“There is something which we don't understand,” he said. “We are quick everywhere else pretty much.
“We know that we have a smaller rear wing, we're compensating what we're losing through the corners. But it's just at high-speed where we're losing all the lap time.”
Wolff explained that the issue goes far beyond just being a set-up problem, as he thinks there is something intrinsic in its car design that is not working.
“I think that's a biggie,” he said. “There's only so much you can tune here.
Source: Autosport