Rashford left United for Villa on-loan for the rest of the season last Sunday.
Giggsy, 51, told The Sun: “Everyone will remember that smile and that enjoyment and freedom when he first came through — but he doesn’t look like that now.
“He’s a human being and he just doesn’t look happy. He looks like he’s got the world on his shoulders.
“He needs to play with that freedom and enjoyment that got him to where he is now."
Now a director with Salford, Giggs also recalled the first time he saw Rashford as a young player at United: “It was basically a small-sided, eight-versus-eight game.
“We saw Marcus go past a few players and put it in the bottom corner and then score another goal.
“Me and Louis (van Gaal) just looked at each other and went, ‘We’ve got to pick this lad — he’s too good’.
“He came into the first team and, of course, scored on his debut and everyone will remember that smile, that enjoyment and that freedom.
“He had a bit of everything. He was brave, he had no fear, he would take players on and would score all types of goals.”