Harrison told the Manchester Evening News: "I cannot believe Danny Welbeck has gone. Okay he might not have been a prolific goalscorer but his work rate and effort was undeniable.
"It is sending out the wrong message when local home grown players like that are leaving. Losing players who have been part of the club since they were young kids means you are losing the heart and soul of the club.
"That's what the Class of '92 were for instance. They were the core and you need that at the centre of your squad."
Harrison admits United's current transfer policy could see them going against the identity they have developed over the past 30 years.
He added: "You need players who have been brought up in the United family and atmosphere. It is special.
"Young players will always want to come to United but they also have to see that there is a road to the first team.
"At the moment the message to them isn't what it used to be. I don't think it has gone forever, I certainly hope not. But I have to say I am worried. United cannot afford to lose their soul."
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