Toro Rosso team boss Franz Tost says the talent of Jaime Alguersuari and Sebastien Buemi was simply not enough to be in a position to challenge for a seat at Red Bull Racing.
Both Alguersuari and Buemi were replaced at the Faenza-based squad in a shock decision by the team, which hired Daniel Ricciardo and Jean-Eric Vergne for the 2012 season.
Tost has stated repeatedly that Toro Rosso's mission is to nurture talent that will fit sister squad Red Bull Racing's demands of a top driver.
And the team boss believes neither Alguersuari nor Buemi were strong enough for that.
Tost also reckons the duo should be thankful to Red Bull for having helped them get into Formula 1.
"This is a high-performance sport and 'departures' are a part of the game," Tost told the official Formula 1 website.
"Both drivers have to thank Red Bull as otherwise they would never have made it into Formula 1. And even now they have it in their own hands to make something out of the chance Red Bull has given them.
"Well, Buemi is still with Red Bull Racing as their third man. What will happen to Alguersuari? I have no information at the moment but, as I said, thanks to Red Bull they have a very good basis to pursue their careers from. Maybe even in Formula 1 at another team.
"I'm not saying that they are not fit for Formula 1 as both have shown substantial talent at some races, but it is not enough for Red Bull Racing.
"But I could imagine that they could be top drivers somewhere else and have a successful racing career."
Red Bull advisor Helmut Marko was quoted as saying that Buemi and Alguersuari would not have been F1 winners, and Tost believes there is a certain degree of truth in that.
"There is probably some truth in Helmut's assertion. When we speak about the 'right stuff' for Red Bull Racing we are talking about a double world championship-winning team, which means that drivers who get elevated there must have the ability to win races and championships.
"And it was from that perspective that second thoughts set in when it came to Sebastien Buemi and Jaime Alguersuari. Toro Rosso is a rookie team - and we will head into the 2012 season with two rookies. I fully support this decision."
Tost also reckons Ricciardo and Vergne will have a couple of tough first races this season, but he is confident in their ability to deliver.
"Both have done extremely well in all the series they've raced in before entering Formula 1 and, yes, they showed potential at the test," he said. "Daniel, with 11 Formula 1 races under his belt and frequent Friday drives with us, has an advantage. But in general I would say that this wow-effect is not so easily manageable in a first season.
"But it definitely has to be delivered in the second season. What I do expect from both is that they deliver solid performances. This means that they have to improve. I don't necessarily mean that they must score points... unless we've built a winning car!
"My guess is that the first four flyaway races will be difficult as neither knows the tracks, but once we come to Europe I expect them to do significantly better. Let me say a final word. I don't have a problem when a driver has a good race and at the next race he has a shunt - that's part of the game.
"Both drivers will have a 'crash period' but that is part of their development phase. It was the same with Sebastian Vettel. But at some point they have to get their game together - and the question is who will be better at doing that? Let's wait and see."
Buemi will be Red Bull Racing's third driver this year, also racing with Toyota in the World Endurance Championship.
Alguersuari is yet to announce his plans for 2012.