An unwell Sebastian Vettel was relieved of his duties at Ferrari on Formula One's first day of pre-season testing in Spain on Wednesday.
The four-time world champion had been given the honour of driving the new SF1000 first at Barcelona's Circuit de Catalunya, with teammate Charles Leclerc not due in the car until Thursday.
"Change of plan: Seb not feeling great this morning so Charles is taking over driving duties for the day," a Ferrari spokesperson said.
The test was the first opportunity to see all the new cars on track together and Vettel joined the other drivers in a photograph on the pit straight before the session started. Ferrari said he had then left the circuit.
The Ferrari-powered Haas and Alfa Romeo teams had earlier pushed their cars out for a pitlane reveal of their new liveries.
The season starts in Australia on March 15, with only six days of testing before then.