There was more bad news for Mercedes on day one of the second test at Barcelona with Nico Rosberg struggling with his fitness.
The team were left scrambling for a driver at the Circuit de Barcelona-Catalunya on Thursday after Lewis Hamilton fell ill and was forced to pull out of the test having completed just 11 laps.
Mercedes later revealed that he suffered from a fever and they were forced to recall reserve driver Pascal Wehrlein, who was testing for Force India on day one, to replace the reigning World Champion.
It was initially thought that Rosberg would take the place of his his team-mate, but it later emerged that the German was unable to drive due to a trapped nerve in his neck.
Rosberg is scheduled to be behind the wheel of the W06 on Friday, but Mercedes have admitted they will adopt a wait and see policy before deciding if he is fit enough.