The Silver Arrows have toiled well off the pace in both the wet-weather FP1 and the dry FP2, placing no higher than sixth in either session.

"The laptime is reality, the stopwatch always tells the truth and the laptime showed we are not quick enough," Wolff said at the conclusion of track action. "It is certainly one of the worst Fridays I can remember."

He told Sky F1: “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, the fronts and the rears, you overheat them and then nothing goes any more. There is a gremlin in the car.”

The German team struggled for pace for much of the preceding race weekend in Singapore, but the layout of Malaysian GP circuit Sepang was expected to play to the W08's strengths.

“You can compare Malaysia a little bit to Silverstone, where we have been very good,” Wolff said. “We've been very good in the high-speed [corners], we are not at all good in the high-speed here.

“There is a fundamental issue in the car that we need to find out. They are very complex, so it can be a tiny detail that just unsettles the car.”

Mercedes' 2017 challenger – the W08 – was dubbed a 'diva' earlier this season due to its narrow optimal operating window, which has been the catalyst for several weak Friday showings and a couple of off-colour races.

Wolff said: “It's a bit up and down with our car. We seem to be performing exceptionally good on some tracks, Monza was one of them where we were a second [per lap] ahead and Silverstone the same.

“And then others where we have these moments where we are lacking the understanding why we are not performing.”

Echoing the sentiments of his team boss, championship leader Lewis Hamilton described his Friday at Sepang as “a very difficult day”.

“I’ve been struggling with the car today, so we have to review and try to understand where we have gone wrong with the balance,” he said.

“We’re hoping that we’re able to find our bearings overnight and regroup for tomorrow.”

Valtteri Bottas, who ended both sessions right behind his teammate in the classification, added: “We’re definitely lacking some performance, it seems like Ferrari and Red Bull are very strong. So we have some work to do if we want to be on the front row tomorrow.

“The car balance itself didn’t feel too bad; it’s just a question of overall grip. The key area we are going to need to focus on tonight will be getting the maximum out of the tyres over one lap.”