Dundee Utd land Aberdeen fullback Duff
"I always admired Stuart when he was with the Scotland Under-21 team and at Dundee United," said Dons manager Jimmy Calderwood. "I have tried to sign him a couple of times and now I have eventually got him.
"It's a great bit of business for Aberdeen. I think he is best in midfield but can also play left-back and a man-marking role anywhere in defence. He is a good passer, has two good feet and is quick."