Charles Leclerc will start the Spanish Grand Prix from the pit-lane after Ferrari made changes to his car overnight.
Leclerc qualified 19th on Saturday and was convinced his car had an issue.
Ferrari confirmed on Sunday it had made changes to the rear end of the car so that a proper investigation could be carried out at the team's Italy headquarters at Maranello.
"We've taken the opportunity to change the gearbox, that's effectively all the backend, really to make sure there's nothing on there that is untoward," Ferrari senior performance engineer Jock Clear said.
Leclerc was convinced his car had an issue after qualifying 19th on Saturday.
"We will have to check the data and most of all check the car because there was definitely something strange," he said. "I nearly lost it during the red flag [in Q1] and I was at 70 km/h and there was just no warning.
"The left-hand corners were really, really bad, with the rear right and I first thought it was the tyres, so we went with a new set of tyres and on the new set of tyres it was the same feeling -- right-hand corners really good, left-hand corners completely off.
"We will have to check, but I would be very surprised if we don't find something on the car."
Williams driver Logan Sargeant, who qualified 20th, will also start from the pit-lane.