Dr Helmut Marko has confirmed that Yuki Tsunoda is on course to make his Formula 1 debut in 2021.
He recently had a seat fitting ahead of his forthcoming post-Imola GP test, which will give him the 300kms of running that qualifies him for a super licence.
When asked about whether any Red Bull junior drivers are ready to enter F1, Marko told Sky Deutschland: "There is only one candidate and that's Yuki Tsunoda.
"He should drive for Alpha Tauri. All he has to do is obtain the necessary amount of points for a super license," Marko added.
"In fast corners he is at Verstappen's level, there are only a couple of corners where he loses a lot of time.
"But if you don't know when and where this happens, then this is a factor of uncertainty that we cannot afford when we are fighting for the title," said Marko.
"If Albon does not live up to expectations, we will have to look outside our team and then Perez and Hulkenberg come into play."