Mercedes was looking distinctly - and very uncharacteristically - far off the pace in Friday's free practice sessions for the Malaysian Grand Prix.
Lewis Hamilton ended the day sixth fastest, behind McLaren's Fernando Alonso. More worryingly for the team was the fact that he he was 1.4s slower than his chief title rival Sebastian Vettel.
While Vettel's time was a new track record, Mercedes was quick to admit that the disparity had mainly been due to a lack of performance on their part
"The stopwatch always tells the truth and the laptime showed we are not quick enough," team boss Toto Wolff told Sky Sports F1 afterwards.
"It is certainly one of the worst Fridays I can remember.
“We struggled from the get-go this morning. In the wet, in the dry, on all tyres. We have to find out overnight what it is.
"At the moment the car is unbalanced and you slide all over the place," he added. "You overheat [the tyres] and then nothing goes any more. There is a gremlin in the car.
“There is a fundamental issue in the car that we need to find out," he stated. "They are very complex, so it can be a tiny detail that just unsettles the car.'
From his vantage point in the cockpit, Hamilton echoed Wolff's analysis of the situation.
"I’ve been struggling with the car today," he admitted. "We have to review and try to understand where we have gone wrong with the balance.
“We’re hoping that we’re able to find our bearings overnight and regroup for tomorrow."
Hamilton's team mate Valtteri Bottas fared no better. He was seventh fastest in the dry afternoon practice, just a few hundredths slower.
“We’re definitely lacking some performance," he said. 'The car balance itself didn’t feel too bad; it’s just a question of overall grip.
"It seems like Ferrari and Red Bull are very strong. We have some work to do if we want to be on the front row tomorrow.
"The key area we are going to need to focus on tonight will be getting the maximum out of the tyres over one lap."
"The car wasn't working as well as it normally has done this year," admitted chief race engineer Andrew Shovelin. "The drivers were both complaining of very low grip and sliding.
"The car hasn't looked strong in any conditions, be it on intermediates or in the dry conditions we had in FP2.
"So we're looking very carefully at the set-up and the configuration of the car just to try and understand what's gone wrong," he continued.
"We are clearly not getting the most out of the package here. We're going to be working very hard to unpick what we've seen today and come back stronger tomorrow.
"But at the moment it's clear we've got a lot of work to do."
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