The 20-year-old Reds hero reckons it was a defining moment in his career. He even earned Fergie's respect with a heartfelt apology in the corridors after the game.
Shelvey revealed: "I still stand by my decision that I wasn't going to pull out of a tackle.
"If I'd done that against United I'd have hurt myself and the fans would have gone mental. But that walk felt like a mile.
"I saw Ferguson in the fourth official's ear so I said to him, 'it's your fault I got sent off,' but I pulled him aside afterwards and apologised because I knew I was in the wrong.
"I was walking back down the tunnel towards the car park and he was walking towards me. I apologised for what I had done and said 'it was wrong and I was frustrated'. I'm a young boy and I think the emotions got the better of me.
"I said I still wouldn't have pulled out of the tackle if it was there, and he said 'it's fine. It takes a man to apologise, no hard feelings. It's an emotional game, don't worry about it'.
"It is a learning curve for me and, to be honest, I am glad it happened. It is something I will be more wary of in the future."
His spat with Fergie ironically helped break the ice after Shelvey's shock England call recently.
He added: "I'd quickly gone from playing in a park with my mates to sitting next to Wayne Rooney at dinner, so I was a bit nervous going in there with England.
"I didn't know what to expect and thought no one would talk to me. It was a bit weird but Danny Welbeck pulled me when I arrived and said 'leave my manager alone'. That helped break the ice."