Harrison, who has died at the age of 81, oversaw United’s fabled academy for nearly two decades and his proteges stuffed the trophy cabinets at Old Trafford and beyond.
His most famous graduates were the ‘Class of 92’ - David Beckham, Ryan Giggs, Paul Scholes, the Neville brothers and Nicky Butt - players who would form the backbone of United’s treble-winning side of 1999.
But they were far from alone. Some 18 future internationals were coached by Harrison, whose tough love methods shaped them into stars.
“It was like joining the army and Eric Harrison was sergeant major,” Giggs wrote in his autobiography.
“I had some real bollockings from him and you couldn’t answer back. He was an intimidating man.”
Harrison was brought to United from Everton by Ron Atkinson in 1981 to work as a youth team manager.
Five years later Sir Alex Ferguson arrived, made him head of youth development, and demanded in return that more players be brought through.
Harrison recalled that conversation in an interview with the Daily Telegraph in 2001.
“I was a bit touchy, because I thought he was having a go at me,” Harrison said. “So I pointed out that Norman Whiteside and one or two others had come through to play in the first team.
“He said, ‘Yeah, I accept that. But I want more than that.’ And when I said, ‘How do you mean, you want more that that?’ he replied, ‘I want more players!’
“So, always having been a bit confident, I said, ‘Right, we’ll do a deal. You get me better-quality players, and I’ll get you more youngsters in the first team.’ And he said, ‘Done!’”
It was the beginning of a relationship that would reshape the club.
The two men grew close, with Harrison understanding just what Ferguson was looking for in prospective first-team players.
“The contribution I always think about with Eric, if you wanted a teacher who gave you the right way, the right path forward, Eric was that man,” Ferguson said in 2017.
“Obviously the ‘Class of 92’ was the climax of his coaching career, but all the young players who came through at that time will always look at the contribution he made and the character he built in these people. He made them good human beings.”
Harrison’s approach came from the lessons he took from his own playing career.
The Yorkshireman began with his hometown club Halifax, where football was an obsession.
On his wedding day, in October 1962, he exchanged vows with his wife Shirley in the morning before playing in a 2-2 draw with Shrewsbury in the afternoon.
After spending seven years in the first team at The Shay he joined Hartlepool, signing a year before Brian Clough took his first managerial role with the club.
Further spells followed with Barrow (twice), Southport and Scarborough, but wherever he went, Harrison felt something was missing - something he wanted to instil as a coach himself.
“In all my career, 550 games over 17 years, not one coach or manager took me to one side and said they would work with me to improve certain aspects of my game,” he later said.
“I was scared to say anything but I didn’t think it was right. I resolved that if I ever got a job coaching, I would make sure the players got coached properly.”
By the time United were lifting the Champions League trophy in 1999, Harrison had started to wind down his coaching commitments, but he later worked as an assistant to Mark Hughes with Wales, and as a scout with Blackburn and Huddersfield.
In later years he began to suffer with dementia, which was diagnosed in 2014. He spent his final years in a nursing home, but was not forgotten by his former charges.
After his grandson Joseph contacted them, the likes of Beckham, Scholes, Giggs, Neville and more turned up to visit and spend time with their old mentor - demonstrating the strength of the bonds he built.
Harrison himself said the manager was the most important man at a football club, but insisted the youth coach should be listed close behind.
In the story of United’s great sides of the 1990s and early 2000s, he was unquestionably right.
“Although Sir Alex gave us our chance,” Butt said, “it was Eric pushing him towards putting us in from an early age.”