Manchester United boss Louis van Gaal let Danny Welbeck leave the club because he felt his goalscoring record was not good enough.
Welbeck, a product of United's youth academy, moved to Arsenal on transfer deadline day for a reported £16million.
The 23-year-old England forward - scorer of two goals for his country in this week's Euro 2016 qualifying win in Switzerland - has netted 24 times in the last three seasons for the Red Devils since returning from a loan spell with Sunderland in 2010/11.
And Van Gaal has made it clear he thinks that is not up to scratch, drawing comparisons with United frontmen Robin van Persie, Wayne Rooney and Radamel Falcao, the prolific Colombia striker the Old Trafford outfit brought in on loan as Welbeck departed.
Speaking at a press conference on Thursday where United's two deadline day recruits, Falcao and Daley Blind, were being officially unveiled, Van Gaal said: "I have given all the players the chance to convince me of their qualities.
"With Danny Welbeck, yes, he was here from when he was nine.
"After coming back from Sunderland he has played three seasons for Manchester United.
"But he doesn't have the record of Van Persie or Rooney, and that is the standard.
"That is why we let him go - also because of Falcao, and the youngsters who can fit in."
The decision to sell Welbeck, coupled with an outlay of around £150million on six new players over the summer, has prompted suggestions that there is a changing culture at United, moving away from their tradition of youth development.
Assistant manger Ryan Giggs has insisted United remain committed to giving youth a chance, though, and Van Gaal on Thursday echoed that sentiment, while also emphasising he has no worries about how he might fit all his players into a coherent system.
The Dutchman, who was a new arrival at Old Trafford himself over the summer, said: "How do we fit all the players in? We bought five players and one is on loan here who we can maybe buy next season, and we let 14 players go.
"So how to fit in these players is not so difficult I think.
"Then, also, we need the youth education, and that is the policy of Manchester United.
"We give youth players a chance. The question is if they take the chance.
"It is, of course, more risky, but I think it is the only way to do it. Manchester United always have grown up players in the squad.
"I have already used a lot of youngsters in pre-season and in the season. I am always willing to give young players chances, but they have to take them.
"The possibility is there, and all the youngsters have to know that. And I believe Manchester United have come to me because of that."
Regarding Falcao, Van Gaal admitted he had already been impressed by what he had seen in training from the man recruited from Monaco but was keen not to put too much pressure on him.
The manager also stressed he had not brought Falcao in due to any notion that Van Persie is a fading force.
Asked if he thought Van Persie is no longer the player he was, Van Gaal said: "No - I think he is now fitter than before the World Cup. I think he is more fit than ever before."
And on Falcao, he added: "When you can hire or buy a player like Falcao, then I don't have doubts because he is for me one of the best strikers in the world, and when you see his record it is unbelievable.
"Today in training he got one ball and it was in the goal. So he confirmed it in his first training session with me.
"But when I say this, I put too much pressure on him, which is not good, because I know it is very difficult to come from another club to Manchester United in a new process."
Falcao and versatile Holland international Blind could make their United debuts in Sunday's Barclays Premier League home clash with QPR.
The game could also see bows for fellow summer arrivals Marcos Rojo and Luke Shaw, and a first home appearance for another, Angel di Maria, who the Red Devils paid a British record transfer fee for.
They are still looking for their first win of the season, having so far drawn twice and lost once in the Premier League and suffered an embarrassing 4-0 reverse at MK Dons in the Capital One Cup.