Mulryan revealed at a sporting awards night of how he managed to get the pair back together at Sunderland.
He told the gathering: "To get involved in Sunderland was never an intention of mine.
"But I was responsible for bringing Roy and Niall together to work again. There was a problem, as you all know!
"What happened was, Niall had come to me and told me that Sunderland were in trouble. They were going to be relegated and they couldn't pay the footballers' wages.
"Although I said that I wasn't interested he convinced me to get a consortium together.
I did that, but we needed a good trainer. We tried Martin O'Neill, but Martin didn't want the job.
So, I said to Niall, 'What about Roy Keane?' He looked at me and said, 'What? He has never trained a team before', and I said, 'Yes, and ye don't talk'.
"I had lunch with Sir Alex Ferguson in London some time before that and he told me that Roy would make an excellent manager, and that on and off the field he was a genius. I told Niall that and he said 'Ok, we'll go ahead'.
"We met with Roy, but Roy didn't realise that Niall was going to be in the room. He walked in, took one step backwards and said, 'What's he doing here?'
"After about 20 minutes, and this shows the strength of the man, he said, 'we had better draw a line in the sand.
"You, Niall, and myself should go out there and sort our differences'. They did and it's all history now.
So that's the Sunderland story and now you know that I was hijacked into it really!" 