Having played under Ferguson Sr and being at Old Trafford since the age of 10, Simpson should know all about the Ferguson effect.
He told the Evening Chronicle: "It's just the way he is - his personality and his character.
"He walks into a room, and you know he's walked in.
"He's had a few goes at me, and I've had my ups and downs, but I've learnt from all of them.
"I've been at Manchester United since I was 10, and I've not just learnt from Sir Alex, but all the other coaching staff. It's a quality club, and everyone who works there has helped me to be where I am now.
"Everyone who has been involved with Man United, and with Sir Alex, takes something with them."