Like Gary Neville, Nicky Butt, David Beckham and Ryan Giggs, Thornley was part of the United team that won the FA Youth Cup, scoring the opener in a second-leg triumph over Crystal Palace that sealed the trophy for the seventh time.
Twelve months later he featured alongside Paul Scholes in both matches of a final defeat to Leeds and within 12 months was making his first-team debut at West Ham.
Unlike his illustrious former team-mates, Thornley does not have a stack of medals to reflect on. In terms of silverware, that 1992 FA Youth Cup triumph was as good as it got.
Thornley did make over 200 appearances as a professional, mostly for Huddersfield and Aberdeen.
But his life at United effectively ended within six weeks of that debut at Upton Park when he ruptured cruciate ligaments in a reserve team game that could easily have led to a place in the Red Devils’ FA Cup semi-final side to face Oldham the following weekend.
“The injury was a killer,” said Thornley. “I wasn’t envious or jealous of the other lads. I knew I was in a profession where injuries do happen. Sometimes it is a pulled muscle. In my case it was a terrible knee injury.
“I realised very soon afterwards imy future was not going to be at Old Trafford, but I still felt I could make my mark at a lower level.”
But it was four years before the umbilical cord to United was severed, the long recovery followed by spells on loan at Stockport and Huddersfield before his move to the Terriers became permanent.
“It is a decision most footballers have to make at some point,” said Thornley. “I had to decide whether to have the prestige of being at United but only ever playing in the reserves or in cup games or be a professional footballer in my own right.”
After leaving Aberdeen in 2002, Thornley had short spells at a number of lower-league clubs, eventually drifting into non-league before retiring in 2010.