Football: Beckham says Welbeck deal is 'sad' for United

England's Danny Welbeck points during a training session at London Colney, Monday, Sept. 1, 2014. England will play Norway in an international friendly soccer match at Wembley. Photo / AP

David Beckham has said Danny Welbeck's departure from Manchester United is "sad" but remains confident Louis van Gaal "knows what he is doing".

The departure of Welbeck on deadline day raised eyebrows, not only for the willingness to sell to a rival, but allowing a promising academy product who has perhaps not fully flourished to depart.

The 23-year-old came through the youth system after joining Manchester United at a young age and went on to score 29 goals for the Red Devils.

His goal return was sometimes questioned and with Radamel Falcao and Angel Di Maria arriving at Old Trafford this summer, Van Gaal sanctioned Welbeck's departure.

David Beckham, part of the fabled Class of '92 that came through the ranks and played a part in making Manchester United the best team in England, admitted the departure of Welbeck was unfortunate.

"We always worry about the young talent coming through, and obviously seeing Danny leave Manchester United is sad," he told the BBC.

"But the manager knows what he is doing, and is doing what he feels is the best for the club.

"Danny, being such a young kid who has grown up at Manchester United now going... I think it is a great signing for Arsenal, of course.

"But I'm not a manager and won't be manager of United in the next 10 years, so it's down to the manager there."

Of the arrival of Falcao, a surprise addition to the squad, Beckham is excited.

"I can only speak from my experience of foreign players coming in, and for me, that is what made the Premier League really exciting - to see young talent from England coming through, but also seeing great players like Eric Cantona and David Ginola.

"Without a doubt it inspired me and gave me great experience to see players like that coming to our league."