Mercedes boss Toto Wolff has said there is a "gremlin" that needs removing after both Lewis Hamilton and Valtteri Bottas struggled for early pace in Sepang.
A much drier FP2 session meant that slicks were able to be used for the first time this race weekend, but Mercedes were left languishing behind Ferrari, Red Bull and even Fernando Alonso's McLaren-Honda as Hamilton and Bottas were off the pace by over a second in P6 and P7 respectively.
Both drivers found the gravel trap in the early stages as they wrestled with their cars and the struggles continued into the qualifying simulation runs as the W08 looked really unsettled through the corners.
"Not blessed," was Wolff's unique take on the session when quizzed by Sky F1.
"It was a very difficult session for us and we struggled from the get-go this morning. In the wet, in the dry, on all tyres.
"The car is unbalanced and sliding all over the place. The tyres are overheating and there is a gremlin in the car."
Wolff was then asked whether there was a bit of a hangover from their opportunistic win in Singapore, but he quickly dismissed that theory.
"They are completely different tracks," he added.
"You can compare Malaysia to Silverstone probably, where we were very good, but there is a fundamental issue with the car that we need to find out."