De Vries was axed by AlphaTauri in favour of Daniel Ricciardo ahead of this weekend's Hungarian Grand Prix after failing to score a point in the opening 10 races of the year.
And although AlphaTauri accepts that de Vries faced difficult circumstances, being a rookie in a uncompetitive car beginning with a run of tracks he had not competed at before, it felt that progress should have come by now.
Speaking at the Hungaroring on Friday, AlphaTauri team boss Franz Tost felt that, without evidence of development from de Vries, and more new tracks coming up in the second half of the year, action was needed.
"This was also a very emotional decision because we have a really good relationship with Nyck," explained Tost. "I just spoke with him on the telephone last week.
"He didn't have an easy time with us. First of all, as a rookie, and this is generally for the rookies also for the future, the first half of the season is not so easy because they are racing at many racetracks which they don't know: like Melbourne, Miami, and Saudi Arabia.
"Then they come to Baku where it is a sprint race, and that means there's only FP1 and then it is already qualifying.
"It means that nowadays, if a young driver comes to F1, he really has to be prepared in the best possible way, which means for me at least 5-6000 kilometres of private testing with an old car, like Alpine did with [Oscar] Piastri. This is the way to go."
He added: "It was difficult for him also, because our car was not so competitive. And if a car is not so good, it's even more complicated.
"I expected a much better performance in Austria and in Silverstone because both of these tracks Nyck knew quite well. But the performance didn't come up.
"And then we decided to change him, also thinking to the second half of the season, where he doesn't know Singapore, Japan, Mexico, Austin, and Qatar, which would not have made it easy.
"Now, with Ricciardo, we have an experienced driver in there, which also helps us to develop the car to find out better where are the deficiencies of the car and hopefully to improve the performance of the car."
De Vries' appointment at AlphaTauri was made by Red Bull motorsport advisor Helmut Marko, and came despite scepticism about the move from Red Bull F1 team boss Christian Horner.
Asked if AlphaTauri should have assessed de Vries more at the end of last season prior to signing him, Tost said: "There was no possibility because he didn't race any more and it was again decided by Red Bull.
"Now, afterwards, everyone is more clever. I think at that time it was a right decision."
