Thornley had been highly rated at Old Trafford and part of the feted 1992 Youth Cup winning side. That game in April 1994 was a sliding doors moment which sent Thornley down the road of rehab and ultimately lower league football, while then teammates Paul Scholes, David Beckham and Gary Neville went on to superstardom.

The early to mid-1990s was still a time when cruciate injuries were potentially career-ending. The celebrated Northern Ireland youth player Adrian Doherty, two years ahead of Thornley in United’s youth setup, had damaged his cruciate and never recovered to play professionally.

It is telling that Doherty is not mentioned in Thornley’s autobiography Tackled . That doesn’t seem like a coincidence, it seems as though the ill-fated Northern Irelander was somewhat blocked from the young winger’s mind in an effort to stay positive during recovery. Thornley now describes Doherty as “a lovely lad but I needed [to focus on] the successes”.

A strong mental attitude was pivotal. He took inspiration from Paul Gascoigne and Alan Shearer, both who had recovered well from such injuries. Niall Quinn suffered the same injury months prior to Thornley and his return also inspired the then United winger.

The injury was not to be the career-ender for Thornley that it had been for Doherty. He did play for Manchester United after his recovery, though he would never fulfil the potential he had promised. Beckham, Scholes and Neville would become first teamers at United, while Thornley was loaned out to other clubs. Ironically enough, he was at Manchester United and on the field when Roy Keane suffered his own cruciate injury at

Elland Road in 1997. Thornley knew immediately the severity of the injury and the dangers Keane faced. He knew the struggle and the mental toughness required. The recovery from such an injury can be grueling, but Thornley knew that Roy had the “fantastic character” to come through it so strongly.

Thornley speaks effusively of his former teammate. He appreciated the little things that Keane brought to the dressing room; his politeness and consistency with people and the fact that he would greet everyone in the same manner each day, regardless of who they were.

There are many things that I loved about Roy and his character and his traits, but the one thing I always liked, being a professional footballer, was having someone who comes in and, even if they don’t have much to say to you, they’ll come in and they’ll say ‘good morning’, or say ‘hello’ and say ‘bye’ if you happen to be passing them. Keaney was very consistent like that.

In Thornley’s view, the people who don’t like Keane take exception to his honesty. In the world of professional footballer, Thornley feels Roy’s level of forthrightness is lacking. Keane would tell it like it is, whereas others might just choose to talk about you behind your back. Thornley contrasts Keane with other high-profile teammates who “are all over you one minute and then ignore you and be in a bad mood the next”.

According to Thornley, there were no hidden depths to Keane: “He was as straight as a die as well as being an incredible footballer.”

The tackle that derailed Thornley’s career is a motif throughout his book and became a demon Thornley confronted on a regular basis throughout his career. He mentions arriving at Huddersfield in 1998 and having to make peace with the fact that a new teammate was a friend of Nicky Marker. Thornley would never forgive Marker, nor would that teammate stop being friends with Marker. The pair just had to accept that and move on.

Which brings us to a certain dichotomy throughout Tackled: That the pivotal moment in Thornley’s career — the Marker tackle — is the kind of tackle dished out by others who he highly regarded. Thornley’s “brilliant teammate” Roy Keane inflicted the tackle that badly injured Manchester City’s Alfe Inge Haaland in 2001.

Thornley sees the contradiction and admits that he cannot condone such behaviour, or any type of tackle beyond the laws of the game. He says he would be a hypocrite to say otherwise.

“I can’t say: ‘Well, the lad who tackled me was a desperate tackle, but because Roy happened to be an ex-teammate it’s okay for him to get away with it.’

“No, it has to be right the way across the board. He knew what he did was wrong, but that’s Roy for you. He makes sure that Alfe Inge Haaland, who he deemed responsible for the injury at Elland Road, got payback, and he made no bones about it. Like I said, that is his character. I would be a hypocrite to say otherwise, because that tackle is beyond the laws of the game and he was rightly sent off for it.”

This tendency to snap was a fundamental part of Keane’s character, says Thornley.

“Like the time up at St James’ Park, when he swung for Alan Shearer and he missed him. I’m not being funny. He didn’t mean to miss him. He would’ve completely forgot where he was, and a bit like the Alfe Inge Haaland thing, he would’ve just thought: ‘Now is my chance, I don’t care that there’s millions of people watching. This is just me and Alan Shearer and I’m going to fucking hit him.’ And he swung for him, and he wouldn’t have cared if he made contact, but that is Roy and you’ll never change him.”

Unlike Adrian Doherty, Thornley returned to football and for this he remains grateful. He played nearly 200 games professionally after leaving Old Trafford. If anything, Thornley’s only regret is not having left United sooner, as he knew he would no longer succeed there.

He appreciates having played with Bryan Robson and Roy Keane, and lauds the impact of Alex Ferguson, Brian Kidd and Eric Harrison upon his career. It’s a healthy outlook. He doesn’t wonder ‘what if?’. He sees such questions as pointless. At 43, Thornley is at ease in his life and appears proud to have played a part in one of the most storied teams of all time.