Mangan used to play with Leicester City star Vardy at Fleetwood Town and has been a childhood friend of Burnley midfielder Barton and says the pair will have some decent insight into Louis Van Gaal's side.
He said: "Joey was actually going to sign on loan until Marseille came in for him. I mean, Marseille or Fleetwood, which one are you going to choose?
"We have stayed close friends for years. He's a great lad, a fantastic professional, someone who you can call upon for advice.
"I'll speak to him about the Manchester United game. I will pick Jamie's brain as well. Things like, where can I go to sort of expose them? It's the mental side as well which is a massive part of football.
"They will have a lot of possession and we've got to be mentally prepared for that and so any piece of advice will be helpful."