Toto Wolff insists that Mercedes junior driver and current Williams Formula 1 racer George Russell is not a contender for a seat with the works team in 2020.
The Mercedes motorsport boss believes it is too early to put Russell, who is in his debut F1 season, in the spotlight alongside Lewis Hamilton and risk "burning" him.
Wolff says Mercedes is facing a straight choice between keeping Valtteri Bottas and promoting reserve driver Esteban Ocon, and he believes that Russell should continue learning at Williams, where he has an ongoing contract.
"You've got to consider that these guys come into F1 at a very young age," said Wolff.
"And there are exceptions to the norm, such as Max Verstappen, who was given the environment at Toro Rosso to learn, and to make mistakes, and even at Red Bull was given [the same].
"I don't think you are given the possibility to learn in a Mercedes.
"Because you're being put in a car that is able to win races and championships, in a high pressure environment.
"It can go terribly wrong for a young driver that has the talent to be become a world champion if he's thrown into that environment next to the best driver of his generation, who has been with us for seven years.
"And I wouldn't want to burn George. Equally I think he's in a very good place at Williams, he helped them to come back to form, learn and appreciate when a car functions well.
"It's these moments [such as Russell qualifying 16th in Hungary] that he needs to learn to appreciate that one day if he's given a car that fights for races and championships - that he appreciates that situation as well.
"I think it would come too early, and on top of that I try to be respectful to all contracts we sign, and we signed a contract.
"We knew what we were doing with Williams, and this is where he's going to learn."
Wolff confirmed that Mercedes faces a difficult straight choice between Bottas and Ocon the coming weeks.
"It's a question between Esteban and Valtteri," he said.
"We've been discussing it for a long time within the team, and I've been wrestling with myself on what is the right thing for the team, and what is the right thing for the drivers.
"And if we were to have only one of them, it would be a no-brainer to have them in the car. And in a way, both deserve the seat.
"At the end what we decided is to not think about it more than we did already, wait for the Budapest weekend to pass, stick our heads together over the summer, and then come to a decision that is best for the team, and best for both, because we care for both."
He made it clear that Max Verstappen is not in the frame: "He's at Red Bull. He has a contract, he's committed to Red Bull, which I like to see.