Dr Helmut Marko has defended Red Bull's notorious driver development program - even though outsider Sergio Perez is replacing Alex Albon for 2021.

It's only a one-year deal for the experienced and on-form Mexican Perez, leaving the door open for Albon or another young driver to race in 2022 after what Marko described as an "up and down" year for the British-born Thai.

"It's not always possible to ensure a seamless supply of talent for Formula 1," Marko told Servus TV.

"But if the others had such a track record such as ours with their own young drivers, I think they would be very satisfied," he added.

"Even the drivers who did not go to Formula 1 with us still earn their money with racing today - in other words, doing exactly the job they love," said Marko.

The 77-year-old Austrian also revealed that Perez's one-year deal leaves the door open for a Red Bull driver to return to the cockpit in 2022.

"If a young driver really matters to us, we have the option for 2022 again," said Marko. "With Yuki Tsunoda we have brought another Japanese into Formula 1 after many years and he is super fast.

"We also have an Estonian and an Indian and absolutely good drivers further down from all kinds of nations."