Manchester United boss Louis van Gaal explained the club decided to sell striker Danny Welbeck after signing Radamel Falcao from Monaco.
The Dutchman was critical of the 23-year-old's lack of goals at the club and highlighted Falcao as one who very rarely misses in front of goal.
"Danny Welbeck had been here since he was nine, but after he came back from Sunderland, he does not have the record of Rooney or Van Persie, and that is the standard," van Gaal said in Thursday's press conference.
"And we have Falcao. Today, in training, he had one chance and it is a goal. That's why we had to let him [Welbeck] go."
With many foreigners joining the Red Devils during the summer, questions have been raised about the future of the club's youth policy.
"The youth is the policy of Manchester United," explained van Gaal.
"When we let go players to other clubs, it is to allow the youth players to have a chance.
"We want to give youth players a chance and the question now is 'can they take this chance?'
"It's of course more risky but Manchester United has always home-grown players in the squad and it's the only way to do it."