Now, almost 21 years later, that talented teenager - namely Ryan Giggs - has won more trophies than any other player in the history of English football and is closing in on his 900th appearance for Manchester United.
As for Irwin, he can't believe Giggs is still terrorising top-flight defences, and recalls when the young Welshman first starting knocking on the first-team door.
"It's incredible," Irwin says as he stands on the forecourt at Old Trafford. "We all knew about him. He was like lightning, he was like the wind, and had such great ability and skill.
"The best thing about him was that he could do his defensive duties as well. He never shirked that responsibility and still doesn't. He played on the left wing in front of me for 10 years and it's incredible he's still as sharp and as driven as he is."
And important to the team. Giggs may be 38 now but he remains a vital component of Sir Alex's championship-chasing side. Games don't get much bigger than United vs Liverpool and Ryan's started all three encounters this season against the men from Merseyside.
The most recent, Saturday's eventful outing, was his 899th for the Reds, leaving him just one short of an astonishing landmark.
"To make 900 appearances for a club like this..." Irwin says, trailing off as he seeks the words to describe Ryan's impending achievement.