The memories have come flooding back for coach McGrain, who was a key man as Celtic knocked Ajax out the European Cup in 1982/83 when George McCluskey scored a sensational late winner in Amsterdam after a 2-2 draw in Glasgow. It was extra special as the magnificent Johan Cruyff was in the Ajax line-up, albeit in the late stages of his incredible career.
"We pumped them," McGrain exclaimed. "But I got the biggest roasting of my life at Celtic Park. Jesper Olsen gave me a roasting. I was like: 'where has this wee guy come from?' He kept running by me and the ball was played inside me.
"Big Jan Molby was playing for Ajax then and he kept putting the ball inside me and feeding it over my head for wee Olsen. It shocked me.
"That got him a move to Man Utd. Everyone who played well against me got a move to Man Utd or Barcelona - I should get a cut!
"Over there you have to do what you have to do. I caught his ankle - not intentionally. I remember Charlie Nicholas got us a great goal over there after the 2-2 draw at Parkhead and then they equalised but George got the winner at the death."
Cruyff, who had masterminded successive European Cup wins for Ajax in the 1970s, was in the twilight of his career but McGrain still relished playing against him.
"He was not as quick as he was but you get old and the best players never lose the ability they had to fulfil passes and pick up people," he said. "He was being used for his experience and his knowledge of the game. If Johan Cruyff shouts at you then you are going to do it. Plus his presence was so mighty.
"I played with George Best years ago in America when football was just taking off there. And you would get the ball and George would just appear in a wee space, and it was easy to find him. Cruyff was the same - it was just great to have played against him."