Christian Horner says Red Bull made a "grown-up" decision to look outside its junior drivers when deciding on its 2021 Formula 1 line-up, where Sergio Perez replaces Alex Albon.
Perez is the first non-Red Bull junior to race for the energy drinks company's eponymous team since Mark Webber was hired to race alongside David Coulthard in 2007.
Since Sebastian Vettel replaced Coulthard after the Scot retired from F1 at the end of 2008, Red Bull has only run other drivers that have been promoted from its Toro Rosso/AlphaTauri sister squad.
But since Daniel Ricciardo left Red Bull at the end of 2018, the team has quickly replaced the two drivers brought in to race alongside Max Verstappen - Pierre Gasly and Albon - who both struggled to close a significant pace gap to the Dutchman.
Speculation over Albon's Red Bull future was high throughout 2020, with the team announcing after the season had finished that it had demoted him to a reserve/development driver role and brought in Perez, who was facing time out of F1 after losing his Racing Point/Aston Martin drive to Vettel.
"It was a tremendously difficult decision, and one that we were fortunate to have time to be able to fully consider - the whole the whole season in fact," Horner told Autosport in an exclusive interview for this week's Autosport magazine.
"And it's highly unusual for a driver of Sergio's quality and ability to be on the market.
"So, we just felt that we would be better placed putting in a more experienced driver alongside Max as we head into 2021.
"I think it was a grown-up view that we took to go outside of the scheme. And to give Sergio a chance.
"Obviously he drove so well last year - particularly in the in the last third of the season."
Regarding Albon's future, Horner said Red Bull will "continue to work with and develop Alex offline", with the 24-year-old also embarking on a part-time DTM campaign in 2021.
"He still remains very much part of the team - he's driving the simulator today as we speak," Horner added.
When asked what Perez's appointment gives Red Bull, Horner replied: "He's got 10 years' worth of Formula 1 experience, I think he's demonstrated his ability to maximise the Pirelli tyre.
"And, of course, he just brings a whole host of experience - of the podiums that he's achieved - and results that he's achieved in cars that have, until last year, been far from competitive.
"I've known Sergio a long time - he drove for my team in GP2 years ago [Arden International, in 2009], and I've always followed his career with interest.
"And it was just a matter of circumstances that presented itself as an opportunity and made sense for Sergio to take the seat alongside Max this year."
The full interview with Christian Horner is included in this week's issue of Autosport magazine, which is available in shops and online