Riley grew up in Lytham, Lancashire, and joined United at the age of six.
He went on to play for the under-18s with Rashford, Scotland midfielder McTominay, now at Napoli, and England goalkeeper Dean Henderson, who is at Crystal Palace.
It was while Riley was playing regularly for the under-21s, aged 19, that he – and 18-year-old Rashford – got their big break in February 2016 under Louis van Gaal.
Having come on as a substitute in a 3-0 win at Shrewsbury Town in the fifth round of the FA Cup three days earlier, Riley was named in the starting line-up for a Europa League last-32 tie with Midtjylland, along with Rashford.
United had lost the first leg in Denmark 2-1 and, missing several key players through injury, were in danger of going out of Europe.
England forward Wayne Rooney was among those out receiving treatment along with goalkeeper David de Gea, winger Antonio Valencia and defender Chris Smalling.
“The day before the game Van Gaal stuck the starting XI on a board at a team meeting,” recalls Riley.
The young player carefully went down the list of familiar names.
Michael Carrick, Daley Blind, Juan Mata, Jesse Lingard, Memphis Depay… Joe Riley!
“I remember thinking: ‘Oh my God’. It was a dream come true.”
Riley’s mum, Derren, and sister, Sophie, were in the 58,609 crowd at Old Trafford to watch him play 79 minutes.
By the time United’s No 49 received a standing ovation when he was replaced by Argentina left-back Marcos Rojo, who was returning after three months out with a dislocated shoulder, Van Gaal’s side were leading 3-1 on the night (4-3 agg), before scoring a further two late goals to book a last-16 European tie with Liverpool.
“I had a really good game but I do remember thinking that could be my last for the first team, because the likes of Rojo and Luke Shaw were working their way back from injuries,” he says.
Riley’s hunch proved correct.
While Rashford went on to play several more times that season, including United’s FA Cup final win over Crystal Palace at Wembley, Riley did not appear again for the senior side.
He continued to train with the first team even after Van Gaal was sacked and replaced by Jose Mourinho in May 2016, and was named captain of the under-23s.
By 2017, however, injuries were already starting to disrupt his career.
A damaged hamstring delayed a loan move to Sheffield United and, when the player did eventually arrive at Bramall Lane, the loan was cut short after he dislocated his shoulder.
Riley’s 15 years at United ended on 25 May 2018, two years after that magical night against Midtjylland.
While former under-18s team-mate Rashford was preparing to go to the World Cup in Russia with England, Riley joined League One Bradford City on a two-year contract.