Formula 1 world champion Lewis Hamilton was forced to abandon pre-season testing in Barcelona with Mercedes due to illness.
The 30-year-old, who pipped teammate Nico Rosberg to the championship last season, managed to complete 11 laps over an hour-and-a-half of the session, but then decided to stop running.
The team confirmed on Twitter that Hamilton would be replaced by Pascal Wehrlein, who had completed 10 laps for Force India that morning.
Mercedes tweeted: "An unplanned stoppage keeping us off track at the moment. @LewisHamilton is unwell and not able to continue driving today, so we're just adjusting the car for Pascal #Wehrlein to take to the track this afternoon. #MusicalChairs."
Hamilton could return for testing on Saturday.
