McDermott has revealed how he spoke to Ferguson junior - Peterborough United boss Darren Ferguson - to see if he could have a chat with the United patriarch and was surprised to be speaking to Sir Alex just a few minutes later.
"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 ahead of the Royals' home clash wth United on Saturday.
"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: "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.
"He has done it, been there, seen it. Everybody's got the ultimate respect for Sir Alex and everything he's achieved."