Isaac Hayden had waited a lifetime for the moment. The midfielder had dreamed the dream and, when it came true, the elation was overwhelming. He was 19 years old, a product of the Arsenal academy and Arsène Wenger had told him he was about to make his Premier League debut. It was October 2014, the fixture was Hull City at the Emirates Stadium and Hayden was in the starting XI. What happened next – in training that morning – would turn his life upside down.

“I remember coming out with the ball, I passed it and then Mathieu Flamini has come in,” Hayden says. “He’s come in and caught me on the inside of my ankle, above the bone, and the ankle has just turned. It has clicked. I actually heard two clicks.”

It was the beginning of a nightmare for Hayden, who now plays for Newcastle United, but he has come to consider it a sliding doors moment. He could not play against Hull – ironically, Flamini replaced him in the lineup – and he would be out of first-team contention for the remainder of the season. Hayden did not get another opportunity under Wenger.

Where one door shut, another opened. He enjoyed a successful season-long loan at Hull in 2015-16, when they won promotion from the Championship via the play-offs, before he completed a £1.5m transfer to Newcastle. The deal contained add-ons worth £250,000. Hayden was part of the team who won the Championship last season and he will fulfil an ambition on Saturday when he plays Premier League football at the Emirates – only not in the colours he originally envisaged.

“The situation with Flamini was not malicious; he didn’t mean to do the injury,” Hayden says. “It was just unfortunate but it was definitely a case of a young pro versus an experienced pro and him saying: ‘Look, I’m still here. This is my position and, if you want to take it, you’re going to have to fight for it.’ Which I was more than happy to do. But with that injury, it was impossible.”

Hayden relives the days and weeks that followed the Flamini tackle in minute detail. Wenger told him to ice the ankle immediately and suggested he come to the team hotel in London later on. The manager did not want to rule him out but Hayden could barely walk and he would stay at home that night. The following morning – the day of the Hull game – he reported for a fitness test. The swelling had subsided slightly and the medical team wondered whether he could play. He was still in pain.

Hayden will never forget his dilemma. If he did not play, would he ever get another chance, particularly in his favoured defensive midfield role? He had made only two appearances for Arsenal – both in the League Cup; the first in midfield at West Bromwich Albion, the second in central defence at home to Southampton. But if he did play and was unable to do himself justice, would that not ruin everything? In the end, the decision was taken for him to sit out the match.

Hayden, left, jumps for the ball with Nicklas Bendtner at West Brom in 2013, one of only two senior appearances by the midfielder for Arsenal. Photograph: Darren Staples/Reuters

“They didn’t scan the injury,” Hayden says. “They just said: ‘It’s OK to play on.’ I said it was sore but they were like: ‘That’s normal on a sprain. It’ll be fine.’ So I did a rehab session and I couldn’t even kick the ball. Every time it touched my foot, I was in agony. So they sent me for an MRI.

“It showed that the ATFL [anterior talofibular] ligament in the ankle had come away from the joint – it was spraying around in the joint – and, if I had carried on, it could have completely ruptured. It was hanging on by a thread. They also said there was a little fissure in the cartilage but that was nothing to worry about. I thought: ‘OK, I trust them with that. We’ll leave that.’ I was out for two months with the ligament.”

Hayden returned in December to play 72 minutes of an under-23 game against Bolton Wanderers. Wenger had recalled Francis Coquelin from his loan at Charlton Athletic as a midfield selection crisis gripped. Coquelin did not force himself into the starting team straight away and Hayden felt the window of opportunity remained open. Then he tried to get out of bed after the Bolton match. He got back in. The ankle had swollen badly.

Arsenal’s medics were puzzled. They knew the ligament had healed and an MRI scan confirmed it. They prescribed a fortnight of rest but Hayden continued to feel pain. So they called on the ankle specialist James Calder, who sent Hayden for a CT scan with a dye injection, which would highlight everything. It picked up a significant flap tear in the cartilage that needed surgery and up to five months out. Hayden’s season was wrecked. “I was just numb,” he says.

Rafa Benítez got two big handfuls of chocolate and he lined them up in formation

By the end of the season, Coquelin had formed a midfield partnership with Santi Cazorla and Hayden could see other players would be ahead of him in the pecking order, including Aaron Ramsey and Jack Wilshere. Mikel Arteta was still around and so was Flamini. It was clear his Arsenal career was over.

What if the injury had been diagnosed earlier? Would he, rather than Coquelin, have established himself at Arsenal, the club he joined from Southend United at the age of 13? Could he have become the imposing defensive midfielder that Arsenal crave?

“Even now, to this day, when I watch Arsenal play on TV …” Hayden says, before tailing off. “I look at Héctor Bellerín, who was in my scholarship intake at Arsenal – he’s the biggest one for me. We were both at exactly the same stage [at the start of 2014-15].

“But when Mathieu Debuchy had his shoulder injury and then did his ankle, and Calum Chambers struggled, Wenger thought: ‘Right, Bellerín is my only option.’ He had a tough full debut at Dortmund and he had a bad game at Stoke but he got his opportunity because there was literally nobody else in the position. Wenger would have had to play Flamini at right-back.”

Hayden tells the story of his Arsenal debut at West Bromwich in September 2013 and how, after Wenger had named him in the squad but excluded him from the team shape drills, he assumed he would be a substitute. When he got to The Hawthorns, it was the kitman, Vic Akers, who told him he was starting. Wenger then dropped another bombshell; he would be in midfield. He had been used purely as a centre-half in training and, even after the game, in which Hayden played well, the manager continued to push him as a defender.

To Hayden, Wenger was difficult to read; his style slightly off the cuff. The contrast to Rafael Benítez is vivid. When Newcastle were made aware Hayden was available, Benítez watched 12 videos of him overnight before deciding to sign him, and the Spaniard made quite an impression on Hayden during their first meeting.

“It was at the Rosewood hotel in London and there was a big bowl of chocolates on the table,” Hayden says. “All of a sudden, he got two big handfuls of them and he lined them up in formation. He started asking me questions. ‘Right, if the ball came in from here and the centre-halves are here, where would you be?’ Sometimes, he said: ‘Brilliant.’ Other times, he said: ‘No. That’s a very English answer.’ It was like a coaching session at the first meeting. After it, I told my agent: ‘I don’t care what it takes. I just want to make this transfer happen.’”

Hayden challenges Leicester’s Shinji Okazaki in the defensive midfield role in which he has thrived under Rafa Benítez. Photograph: Owen Humphreys/PA

Benítez takes meticulous to the next level. According to Hayden, the manager has written a thesis on the holding midfield role – a comparative analysis of the position across five countries, including England and Spain. Hayden thinks Benítez studied it at university in Madrid.

“He’s literally obsessed with it,” Hayden says. “He played that position himself. He wants to talk non-stop. I could play really well and he’ll never say: ‘Well played.’ He will always tell me I was out of position by two yards in a particular situation. It’s just how he is. You have to be bang on it in every way.”

When Hayden moved to Newcastle, he lived in the same apartment block as Benítez. “I’ve moved out now,” Hayden says. “I’d get my dinner from a restaurant around the corner, which did lovely chicken and pasta dishes, and I’d collect it after training. He’d come home at the same time and he used to catch me as I got out of my car. One time, I was sitting in the car, waiting and waiting for him to go up in the lift but he was waiting for me. My food was getting cold. He’d just want to talk about football for half an hour.”

Hayden is mature beyond his 22 years. He is engaging and expansive – it is easy to see how he left school with 13 GCSEs – and, unlike some of his peers, he is self-critical and volunteers strident opinions. Having represented England at every youth level, his ambition is to make it to the seniors.

He has come to appreciate how and why football is akin to “religion” in Newcastle – to borrow the word he uses – and, game by game, the pressure on him and his team-mates is immense. He is not one to shy from a challenge.

“The target for the season has to be survival,” he says. “The club has so much potential but it’s never going to be realised under the current ownership. I don’t think it’s because Mike Ashley doesn’t want to realise it. I think it’s that he can’t afford to fully realise it. Look at the Man City owners or the Glazers at United. The money that has to be spent in the Premier League, just to be competitive at the top end of the table is absolutely crazy now. He’s just not in that league and he genuinely cannot compete.

“He’s trying to sell and it will be amazing for Newcastle when the takeover happens but in the meantime, it’s up to us to stay in the league. We can do that, especially with Rafa as manager. Realistically, we can aim for 12th and up. It’s about getting it right and if we stay in the league, as I believe we will, everything will come together.”