Manchester United boss Louis van Gaal says striker Danny Welbeck was sold because he did not score enough goals.
And the 63-year-old Dutchman insists he will give home-grown players a chance.
"He played three seasons for the first team, but he doesn't have the record of Robin van Persie or Wayne Rooney. And that is the standard," Van Gaal said.
"That is why we let him go, because of Falcao, but also to allow the youngsters to fit in. That is the policy. That is why I am here."
Welbeck joined Arsenal on transfer deadline day in a deal Gunners manager Arsene Wenger revealed almost did not happen.
The Manchester-born forward, who scored both goals for England in Monday's 2-0 victory over Switzerland, netted 29 times in 142 United appearances.
Welbeck's international team-mate Rooney, 28, has scored 217 goals for United in 445 matches, while Dutchman van Persie, 31, has hit 48 in 78 games.
United spent close to £150m during a summer transfer spree, but also allowed a large number of players to leave.
Van Gaal said promoting local young players was a cornerstone of his philosophy at Old Trafford.
|Man Utd's last hometown hero|
|BBC Sport's Simon Stone: "Longsight-born Welbeck was the only Mancunian remaining amongst the senior players in the United first-team squad. He caught the attention of club scouts when he was just six years old and joined their academy when he was eight."|
"We let 14 players go, we have only brought six players in," he added. "That means there are many positions vacant, they are vacant for the youth.
"I have already used a lot of youngsters in the season and pre-season, so I am always willing to give young players chances - but they have to take the chances.
"The possibility is there. All the youngsters have to know that."
Much of the attention during Thursday's news conference focused on Falcao.
The Colombia striker hinted he wanted to stay at United beyond his season-long loan from Monaco, with the Old Trafford club having an option to buy him for £44m (55m euros) in the summer.
"This is a new process, a new team," the 28-year-old said.
"I would like to be here and part of his project. Every player wants to play Champions League.
"This year it is not possible in Manchester, but we are confident to achieve the qualification for the next season."
Van Gaal praised Falcao, adding he believed he could lift United to new heights.
"When you see his record, it is unbelievable," he said. "Today in the training session, he got one ball and it was in the goal.
"When I say this I put too much pressure on him, I know it is very difficult to come from another club to Manchester United in a new process."