Toto Wolff says Mercedes are on a "razor's edge" with their 2023 car after a wildly inconsistent Friday in Miami.
The Silver Arrows started the day well, finishing 1-2 in FP1 with George Russell leading Lewis Hamilton.
However, FP2 was a different story, with Hamilton only seventh and Russell down in 15th.
Both drivers were seemingly unable to find any speed on their low-fuel, Soft tyre runs towards the end of the session, and Wolff acknowledged that the W14 had proven to be a tricky beast to tame.
"I think the car has some goodness, it's just very tricky to unlock it from a setup point of view and also driving it," Wolff told media, including RacingNews365.com.
"If the drivers have confidence, both of them, the car can go quick, but it's on a razor's edge and when we are a little bit beyond it, then the car is really difficult.
"It's unpredictable, it steps out under braking, understeers. I mean, it does the whole thing.
"[In FP1] this morning, we seemed to be in a sweet spot of the car. I don't think that you can extrapolate from this result; we ran later than everybody else, but at least it looks more encouraging than Baku."
Hamilton in particular had voiced his disappointment with the performance of the W14 at Miami, saying it felt like driving last year's car, and Wolff admitted that the W14 did not inspire confidence in its drivers.
"I think a good car is a car that the drivers are able to push and feel that it doesn't do anything unpredictable," said Wolff.
"Unfortunately, over the last year, and this year, particularly in qualifying, where you really need to push the limits, the drivers couldn't find any confidence in the car."
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