Clues about Mercedes' lack of pace compared to Red Bull emerged on the final day of F1 pre-season testing, with Lewis Hamilton unable to prevent Red Bull from topping the timing screens.
With Mercedes hampered by poor handling and reliability issues on the second day of testing, the team recovered to register 148 laps of the Bahrain circuit and set the second-fastest time.
Despite the car appearing to be easier to handle on the third day of the test, the team were unable to challenge Red Bull's chart-topping lap time.
The Red Bull also managed to set the fastest time on a harder compound than Mercedes which, despite the usual caveats of not knowing how much a team is 'sandbagging', could point to a fundamental pace disadvantage for Mercedes.
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Mercedes: Work to do on car pace
Speaking after an improved showing on the final test day, Mercedes Trackside Engineer Andrew Shovlin conceded that the team would aim to extract more lap time from the car, after their day of improving the setup.
"A fair bit of work took place overnight to find some refinements to the car specification and recover our direction on the setup," commented Shovlin.
"We do seem to have made progress; both drivers felt the car was in a much better place across the range of conditions today and the balance is closer to what they require on single lap and long run.
"It's clear that we still have work to do on car pace but today has given us a much more coherent picture of where we need to focus our efforts.
"We'll be using the time ahead of next weekend to go through the data we've collected, and aim to extract a bit more lap time."