Mercedes admits it has a “long journey ahead” to establish and understand the poor handling and balance characteristics that plagued its 2021 Formula 1 car during pre-season testing.

The reigning world champion’s updated W12 challenger appeared skittish and unstable throughout the three days of running in Bahrain, with Valtteri Bottas reporting the rear-end of Mercedes’ 2021 F1 car was “quite snappy and unforgiving”.

Both drivers' struggles to keep their car on-track were evident when Lewis Hamilton suffered a pair of spins on consecutive days, losing the rear of his W12 at Turn 13 on day two, before pirouetting once more coming out of the final corner as he geared up for a flying lap on Sunday evening.

In contrast, Red Bull’s RB16B looked particularly drivable as Max Verstappen ended winter testing with the fastest time. Mercedes strategy director James Vowles conceded the team is yet to get to the bottom of its troubles.

“It was pretty evident that the car was handling poorly and conversely the Red Bull in fact looked what we would call planted, but it was a very stable car especially through the last sector of the lap,” he explained in a Mercedes pre-season test debrief video.

"And I think that's a fair observation, it was visible to the outside and I would say the lap times mirrored that as well. But it's also fair to say that we don't have answers as we are sat here now, it is just 24 hours after the end of the test.

“[We have] huge amounts of data available to us and now a long journey ahead to try and understand what was causing that.”

Mercedes trackside engineering director Andrew Shovlin admitted the drivers were having to “work pretty hard to do the lap times that they were doing” across the three days due to the problematic rear-end, something he hopes can be addressed in time for the season-opener.

“The wind made it tricky, when the wind is behind the car you lose a lot of downforce because effectively the air speed is reduced so some corners where the wind was behind,” Shovlin said.

“It was prone to doing that, and then also the tyres are quite easy to overheat on that circuit and if you start sliding, you tend to lose grip and it gets worse. So, there are a few problems.

"Now, importantly we could see that some of our competitors weren't struggling in the same way as us, so we need to put quite a focus on understanding why the rear end was a bit weak, how we can get it more stable and predictable and that work is going on now.

“Hopefully when we get to the race weekend it won't be so difficult for the drivers because they were having to work pretty hard to do the lap times that they were doing.”