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 German, a four-times world champion, had been given the honour of driving the new SF1000 first at Barcelona's Circuit de Catalunya, with team mate 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,” said a spokesperson for the Italian team.
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.
British driver George Russell, in the Williams, was first out in a major improvement from last year when the team were unable to get a car to the track in time and eventually turned up three days late.
Poland's Robert Kubica, Russell's departed 2019 team mate, returned to the track as Alfa Romeo's reserve driver, while Frenchman Esteban Ocon, who had a year out last year, was back for Renault.
The 2021 rules are little changed from last year, but one difference was a new decree barring teams from hiding their cars behind screens in the garages, giving fans in the stands a better view.
After an hour and 45 minutes of the opening session, Mercedes' Valtteri Bottas was top of the time sheets.
Bottas's world champion team mate Lewis Hamilton is hoping to equal Ferrari great Michael Schumacher's record seven titles this season.
The season starts in Australia on March 15, with only six days of testing before then.
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