The 51-year-old Reading boss will welcome the 19-time English champions to the Madejski Stadium on Saturday, with the Royals searching for just their second Premier League win of the campaign.
And McDermott, who led the Royals to the Championship title last term, spoke of how the United manager came to his aid last season after he had contacted Ferguson’s son looking to speak the Scotsman.
“I spoke to him in January about something that I needed to address and he was very helpful to me and giving me good advice,” said McDermott.
“I spoke to his son and asked him if he wouldn’t mind Sir Alex giving me a ring. And, five minutes after that conversation, a private number came up and it was him.
“So, that just tells you the calibre of the man and what he’s about.”
He added: “That’s between him and me and obviously just talking to him was good for me.
“I don’t know him particularly well but I just know him from that instance and I know that he’s done that with a lot of young managers in the past. He does a lot for football and he does a lot for people in the game, and everyone respects that.”