Brian Clough used to like it here in the 1970s. It was here that his Derby County team discovered that they had secured the English league title in 1972. Later on at Nottingham Forest, Clough and his assistant Peter Taylor became so fond that they came to refer to this place as their ‘branch office’. Here is Cala Millor, the Mallorcan resort and nearly 50 years on, Cala Millor is less invigorating.

It is three days before Christmas and, out of season, Cala Millor bears all the scars of a ghost town. A desolate melancholy grips the deserted stretches of sandy, wind-blasted beach. Local restaurants have the shutters down. Visitors are invariably retirees, a German couple here, a Russian septuagenarian there, a few bridge-playing British widows in the ballroom of the hotel in the evening.

In the poolside bar, a footballer glances around. He is not a player you would know by sight. Only the swottiest of football anoraks would know him by name. Many of the players and coaches interviewed for this book admitted they could not recall him at all. Yet Lionel Messi should know his name. Once upon a time, he was Lionel Messi’s captain. Now, he is 33, retired and a hotel receptionist. He is Arnau Riera.

Brian Clough was a fan of Cala Millor in the 70s but it is very different now (Getty)

His story is a sad one; the narrative of potential unfulfilled, of the uncertainty of sport.

Riera grew up in Real Mallorca youth sides before being scouted by Barcelona, where he was recruited aged 19 in 2000. Riera explains: ‘I scored against Barcelona twice at youth level. I fitted their profile. I was a good passer, a quick thinker, looking to break the lines, in the Pep or Busquets pivote mould. I signed a deal worth around €700 per month and lived in one of the dorms overlooking the stadium. I went into the Barca B team, with Iniesta, Thiago Motta, Victor Valdes, Oleguer Presas – a bloody good team. I played every game and we were champions.’

Riera became B team captain. In a 2004 poll in Mundo Deportivo, he was tipped to become the next player to break into the first team. Then, a little Argentine came along. ‘At Barcelona, kids always arrive with big talent. We’d heard the stories but Lionel Messi was only 16. I remember a very fast, agile player but very introverted. When he picked the ball up, he blew our minds. Normally when a kid comes in from the younger age group, they shrink when they have to take more responsibility. For him, it was natural. It was like he was immune to pressure. He just played for fun, like a toddler doing a jigsaw. I was always more anxious. My biggest handicap was I thought too much. I spent too long thinking about what could go well and what could go wrong. We had sports psychologists to improve performance, both individually and as a group. I depended on them. Messi worked with them, too.’

Riera saw his teammates disappear one by one, over the horizon into the first team. Then Frank Rijkaard invited Riera to join pre-season in 2004. ‘We were in the mountains. Barça B had a high level but the first team was in the stratosphere. There was Ludovic Giuly, Samuel Eto’o and Ronaldinho. They signed Deco that summer from Porto. We are talking about superstars. I really struggled with the rhythm of it all. It was a whole different speed of thought, speed of movement, reaction time, everything. The atmosphere was hard, too. You have to earn their respect and that’s hard. It’s all that masculinity stuff. The dressing room is driven by testosterone and you have to respond. If you don’t respond then it’s very difficult.’

Ronaldinho, Deco and Samuel Eto'o arriving in Barcelona meant Riera leaving (Getty)

He pauses, taking a sip of coffee. ‘If I’m honest, I felt isolated. It’s just . . . I saw them as great players and wanted them to think the same about me. I knew they didn’t really. It was quite a cold feeling. I wanted to belong but I didn’t belong. I wanted to prove myself but I couldn’t. You’d say a few pleasantries with them all but my relationships didn’t warm up.’ I wonder if more could have been done to help the integration, whether it is a healthy environment for young people? ‘In general, there is individualism. It’s weird. You ask me what I miss most about football and it is being in a dressing room. Yet it was also the hardest thing in football.I had a few squad selections with the first team. I never really believed I could make it. I saw how high the level was. I don’t know if I maybe lacked enough ambition. I came from a little village and had smaller expectations. I arrived at a club with extraordinary social dimensions. It was like I had vertigo, dizzied by the heights I needed to scale. You arrive in the squad, get to the stadium and it was daunting.'

Riera did not become a Barcelona star, but there is no shame in that. English football’s recent history is littered with examples of players who had to leave their Barça education behind and embark on adventures in the Premier League. Mikel Arteta and Pepe Reina are examples. Arteta grew up in San Sebastian, the picturesque Basque town. Yet aged 14, he left his hometown behind for Barça.

‘Twenty years ago, this wasn’t normal but my parents knew that my dream from a really young age was to sign for Barcelona. I remember a passion stirred me as I watched them as a kid. I don’t know how to explain it – but it excited me, it made me smile, it made me want to be like them: Michael Laudrup, Pep Guardiola, Romario, Ronald Koeman, Hristo Stoichkov and then later the Brazilian Ronaldo . . . the list goes on. I wanted to form part of this amazing tapestry. I saw Barcelona as the most beautiful expression of football. I’ve always felt that you should be happy doing what you do and the style Barcelona play is the one most capable of putting a smile on your face. My parents knew they didn’t have a say in it. There would be no “wait and see” or “maybe you should stay?” No, no, no. I had been training a bit with Bilbao and my parents tried to argue the case but I was 14 and had it very clear.

Pepe Reina was also let go by Barca, but would taste success with Liverpool (Getty Images)

‘Leaving my family was very, very difficult. I arrived into a strong age group, though, and we formed a really close relationship. Pepe Reina was on the same bunk beds as me, him on top, me below. There were times we all needed each other emotionally. You miss your parents, your family.’

Reina recalls similar anxiety upon joining La Masia. ‘I remember the date: 28 August 1995. I was 12 years old, ten days short of my 13th birthday. I just remember being nervous, like really trembling. I was moving out of my home. I arrived there alone and it was scary. You think, “Am I good enough?” “Will they like me?” I started receiving these long letters from my parents and they were making me upset because I was hankering for home. In the end, I had to plead with them to stop sending them because I was going to become homesick. I said to my parents, “We can talk on the phone but really, that’s it.”’

Arteta is now a highly-rated coach despite failing to make the grade with Barca (Getty)

Arteta continues: ‘In our dorms, there was Reina, Valdes, Iniesta and Carles Puyol. I remember there was this guy called Haruna Babangida. Wow, at the age of 15 he was the best player in the world. I cannot put into words how talented he was. He ended up in Greece, Cyprus and Russia. He should have been a star.' Arteta shakes his head as he recalls Babangida’s untapped potential. It must be a strange adolescence at La Masia, where every friend is a rival, where teenage impulse is inhibited. ‘We had very strict rules,’ Arteta says.

‘But when we were able to, we did certain things. When you’re 15 years old, you have certain needs! You are discovering yourself, the hormones are going crazy and it’s a process. It’s an academic test as well, because our days were split between school and training. It’s painful when it’s very clear that a kid won’t come good for reasons beyond his talent. All you can do is guide, warn and advise but if they don’t want to listen and can’t change . . . then that’s their problem. If you’re in an environment and if you have everything you need, all the tools to succeed and know it’s your dream and you throw it all away, then it’s clear you don’t want to make sacrifices.’

Arteta joined PSG at 19 before playing for Rangers, Everton and then captaining Arsenal. Riera’s experience is more jarring. In 2006 and aged 25, the time came to leave Barcelona.

From Guernica to Guardiola: How the Spanish conquered English football - out now (Simon &amp; Schuster) (Simon & Schuster)

‘Sunderland came in out of the blue,' Riera says. ' My friend Andy Mitten [a journalist] was walking back with me from the stadium to the hotel one day. We stopped by a pub and got talking with fans. One guy happened to be letting a flat. It was a nice apartment near the sea in Sunderland. Lots lived in Durham but I wanted to be close to the fans, to feel the club.

'Sunderland were in the Championship and in total chaos. This was nuts. Niall Quinn had become chairman but was also the manager. That didn’t last long. I’d never seen that before . . . Imagine Jose Mourinho as president and manager! The results went badly. The training sessions were poor. I spoke with my dad and I told him we were losing because we were training like an amateur team. It wasn’t good enough. The methodology was poor, it was badly organised and we trained without the right tactical and physical preparation. There was nobody to physically prepare us. It was just games in training without objectives. I don’t want to sound arrogant but imagine that compared to Barcelona. We needed to do defensive shape and work on the transition. Given the size of the club and ambition and the capacity of the stadium, it was poor to see. Sunderland have a bigger stadium than Valencia, probably the fifth biggest team in Spain. They are always in a relegation battle or in the Championship. The area deserves better.’

Roy Keane had no time for Arnau Riera at Sunderland (Getty)

Four games into the season, Roy Keane arrived as manager. ‘Roy had clear ideas. I was sent on loan to Southend for a month. Keane didn’t want me and he was honest. He called me in. I had been sent off in a cup game in my second match. It was a stupid action. I was too desperate to impress and overcompensated. Straight red and a four-match ban that coincided with Keane’s arrival. Keane didn’t give an explanation. All he told me was I wouldn’t be part of his plans.

‘It was a massive shock. I’d signed a three-year contract and moved country. I had grown up watching Roy Keane and was so looking forward to learning from him. The only time Keane really spoke to me was when he needed a couple of extra players for a training session to make up the numbers.’

The one-month loan to Southend was a failure and he then headed north of the border to Falkirk. 'I scored a brilliant goal against Rangers at Ibrox. There was a fun tradition where we’d play crossbar challenge and then you’d jump into the mud at the wettest time of year. I started working with the Carrongrange School in Falkirk. It was a school for children with additional support needs, where I volunteered one day per week. I am studying for a qualification in social education.’

Arnau Riera was Barcelona B captain, but things didn't work out for him in Britain (Getty)

After Falkirk, he joined Atletico Baleares in Mallorca. ‘I suffered a terrible, horrible injury – a cruciate ligament injury. Everything became more difficult. I knew that was the end at the highest level. They operated on it and during the recuperation period, I went to Sunderland and used their facilities. Niall Quinn let me use it all for free and I stayed with Julio Arca.

‘When I recovered, I then damaged the other knee because I overcompensated. The knee ligament injuries are real bastards. Six months, at least, the muscles need strengthening. It destroys your confidence. Things you took for granted before, you think twice about after. Can you whack a shot from 25 yards? Can you slide-tackle? In England, you can’t have that at the back of your mind. You have to be all guns blazing, 100 per cent to succeed.

Lionel Messi and Pep Guardiola are two of La Masia's most famous success stories (Getty)

Aged 31, he retired. As Messi lifts his ninth La Liga title this season, Riera works in a local hotel on reception while completing his studies. 'For a while, there was this bleak vacuum. Little by little, I had other muscle problems. It was a natural decision to stop. It killed me but I felt I had to. It was so hard. I loved football as a kid. It’s my life and will always define me. As a child, I read the magazines and collected stickers, talked tactics with school-friends, grew up worshipping my idols. My frustration is that I never reached the level I could have done. I didn’t approach it, in truth. Now I am ending my studies in social education. It is fascinating and I need to work.’