Arguably the best full-back of his generation, McGrain now holds down a first-team coaching role with Neil Lennon's side.
And he believes that many of the club's youngsters can learn from the senior players simply by training alongside them - just as the likes of he, Davie Hay and Kenny Dalglish did when they were invited into training with the Lisbon Lions.
"They weren't there to give us advice, we just trained with them," he said. "They were there if we wanted to ask them something but myself, Kenny and some of the others were still too much in awe to ask them anything.
"We were training with them, though, and wee Bertie Auld, Jim Craig, Billy McNeill, Bobby Murdoch, they would all talk to you. They'd talk to you about their families and you'd get to know them better. They were a great bunch of guys and we learned from that, and the training sessions, unknowingly.
"I started as a left-midfield player but I grew into a full-back due to the fact I watched the likes of Jim Craig, Billy McNeill and Bobby Murdoch, their stuff stuck to me," he continued.
"When we trained with the first team I played against wee Jimmy and it was a nightmare. I hated playing against him because he always roasted me. I was 18 at the time and I was stupid enough to try and kick him.
"Sometimes I was unlucky, sometimes I got him, but if I did he would just get up, rub his head and get on with it. And again, that taught me, I was learning things without realising what I was learning.
"You're not aware of what is happening but when you take it all in I'm so appreciative of what these players did. They weren't trying to teach you anything, they were just doing their natural thing."
And McGrain has also revealed that he can still recall the nerves when he first began training with Jock Stein's side.
At the time Celtic were a team made up of players who had just won the European Cup and who were the oustanding talents of their generation.
But McGrain was soon to come to appreciate that they were without too many airs and graces. It is difficult to envisage the modern equaivalent being quite so laid-back and enthusiastic when it comes to welcoming youngsters into the fold.
"At the time it was very nerve-wracking," he told Celtic TV. "I remember training at Celtic Park and we would do a warm- up of four laps around the pitch.
"I would be at the back with Kenny Dalglish, I was about 17 years old and he was 18. Billy McNeill was at the front and we were talking to each other, whispering, 'That's Billy McNeill up there!'
"After watching the European Cup, and having been part-time for a year, we were now on the park, running around the track with that squad.
"Everyone trained together, wee Jimmy was there, everyone. And after the first lap I thought I was going to wake up, it was so surreal. The players took us into their fold, wrapped a big blanket around us and looked after us for the next two or three years."
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