Former Toro Rosso driver Jaime Alguersuari has labelled the Red Bull junior programme's treatment of young drivers as unfair.
The Spaniard became the then-youngest driver in F1 history when making his debut at the 2009 Hungarian Grand Prix having been promoted through the Red Bull junior ranks.
But his time in the sport came to an end in 2011 having been moved aside for Daniel Ricciardo and Jean-Eric Vergne and despite a short spell in Formula E later in the decade, Alguersuari gave up on racing aged only 25.
After Nyck de Vries was ousted in favour of Daniel Ricciardo for the remainder of the season at his former team, now AlphaTauri, Alguersuari told the Sky Sports F1 Podcast: "The way they [Red Bull] act is sometimes not fair. What they did with me and Buemi was not a very generous, sporting manner to get rid of two drivers.
"It was not decided on results, it was decided on commercial and other interesting things. But that's the way F1 works and you have to accept it.
"But, I had a good time with them and I enjoyed every single moment. But even the pressure moments are fine. If you cannot deal with the pressure, you cannot deal with the moment you have a winning car and are about to become World Champion. You have to deliver."
I agree with the way they work
Between Alguersuari and de Vries, nine other drivers had participated in F1 Grands Prix for the Red Bull-affiliated team.
Of those nine, only Verstappen has gained a foothold in Red Bull's operation, with the rest forced to rebuild their careers elsewhere.
"I agree with the way they work," added Alguersuari.
"I just don't agree with how sometimes they apply things to some drivers.
"If you don't deliver results and are not where you should be, they have the right to get you out because they are asking you for the best."