Nico Rosberg did not replace unwell Mercedes Formula One teammate Lewis Hamilton in today's test because of an inflamed nerve in his neck.
World champion Hamilton kicked off the team's four-day test at Barcelona, but had to pull out after a handful of laps because he was not feeling well.
The Briton was not replaced by Rosberg, however, but by reserve driver Pascal Wehrlein, who had been testing for Force India until then.
The Silverstone-based team had to call up Sergio Perez to drive in the afternoon.
Rosberg did not take to the track in place of Hamilton because he was advised by doctors to rest to recover from the nerve inflammation.
The German is scheduled to drive in the test tomorrow.