1) Hidetoshi Nakata

You can tell a lot about a player in Italy from their nickname. Javier Zanetti was labelled “El Tractor” while Alessandro Del Piero was “Pinturicchio” – “The Little Painter”. With his everchanging crop of hair, Hidetoshi Nakata always stood out on the football pitch, and his obscene amount of talent quickly won over fans at Perugia and Roma (with whom he won a Serie A title), who all referred to him as “The Little Jewel”. Off the field, he was a marketing dream and on the day his £18m transfer to Parma was announced in 2001, an estimated four million people tried to access his homepage. But those that make a greater mark leave a bigger void and when Nakata announced his retirement at the age of 29 after the final match of Japan’s World Cup in 2006 against Croatia, in which the three-time Ballon d’Or nominee had been named man of the match, the world was stunned.

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“I decided half a year ago that I would retire from the world of professional football,” Nakata wrote, before later admitting: “Day after day I realised that football had just become a big business. I could feel that the team were playing just for money and not for the sake of having fun. I always felt that a team was like a big family, but it stopped being like that. I was sad, that’s why I stopped.” Adored in Japan, Nakata continued to have huge sponsorship deals and worked as both a model and an ambassador for various charities in his 30s. Aged 39, he now runs a sake company.

2) David Bentley

David Bentley played football in the wrong era. Had he ended his career when he first made an appearance for Arsenal in 2003, playing in the 1990s when footballers could live a more lenient lifestyle, one suspects that he would have earned many more than seven England caps and would have played well into his thirties. Instead, at the age of 29, he called it quits, citing disillusionment with the game. “When I first started at Arsenal when I was 15, there was Ray Parlour, [Tony] Adams, and it just used to be fun. It’s not like the real world, it’s a privilege to go in every day,” Bentley would later explain. “But you’d be a bit scared. Your car would be nicked, or your clothes would be chopped up. It was fun stuff happening. Now it’s a little bit robotic. The social media side of it has made it boring and predictable and calculated. To go and sign for another three or four years, it wasn’t really an option for me.”

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There are plenty of stories of Bentley playing up. Jimmy Bullard once told the story of when he and Bentley became embroiled in a competition in the England canteen, where they took turns to see how loud they could say Postman Pat in front of Fabio Capello, then England manager, without the Italian noticing. “Fabio walked past and I said ‘Postman Pat’, he hardly heard it,” recounts Bullard. “Bents went straight up to his boat, I’m talking inches away, and shouted ‘POSTMAN PAT AND HIS BLACK AND WHITE CAT’. Fabio asked: ‘What are you on about David?’ Bents replied: ‘Ya know, Postman Pat, you look like him. Big dish.’”

There are also reports that Bentley was crowdsurfing at V Festival the day before meeting up with England. Wearing jeans and pointy smart shoes, he once bet an agent £15,000 that he could land a football in a skip from atop of a multi-storey building in Tottenham Court Road, and duly obliged. None of this is curated to garner a cult following, or promote a brand, or sell an autobiography. This was just a normal lad with money in his pocket, mucking about for a laugh.

The best footage of Bentley, though, is on the field. He was never particularly quick, or athletic, or hard-working, but many hold the opinion that only David Beckham owned a more potent right foot at that time in England, and it was not a shock to see Tottenham pay Blackburn £15m for him in 2008. His first career goal (with his left foot!) in 2004 was an impudent chip for Arsenal from outside the box, but he will be best remembered for another lofty effort, this time against his former club: volleying a 45-yard shot into the top corner for Spurs in a 2008 north London derby.

Many argue that Bentley wasted his talent, but anybody of the opinion that he didn’t care enough should listen to his retirement announcement, in which he simply called up Sky Sports News and choking back tears, said he had fallen out of love with the game. He was a fabulous player.

Facebook Twitter Pinterest David Bentley in full flight for England at Wembley in 2008. Photograph: Tom Jenkins for the Guardian

3) Mário de Castro

Perhaps you have never heard his name, but no other player in the history of professional football has a better goals-to-game ratio than Mário de Castro. His 1.95 goals per game (195 in 100 appearances) put him streets ahead of Pelé (0.96) and well clear of his nearest rival, the great Fernando Peyroteo (1.68). After forming one third of what was referred to as “Trio Maldito” or “The Unholy Trio” at Atlético Mineiro between 1926 and 1931, alongside Jairo de Assis Almeida and Said Paul Arges. One of five siblings to a widowed mother, who initially did not know of her son’s exploits due to him playing under a pseudonym “Oriam”, De Castro was notoriously stubborn and once turned down the chance to represent Brazil at the 1930 World Cup – which would have made him the first player outside São Paulo or Rio de Janeiro to represent his country – because he was not considered first-choice.

A commitment to principles would ultimately end his football career in 1931. Needing a victory to seal their third state title in six years, Atlético found themselves 3-0 down at half-time to Villa Nova in the final match of the season. Four second-half goals from De Castro turned the tide but as Atlético celebrated a remarkable 4-3 win and their championship, one of the club directors shot and killed a Villa Nova fan. A qualified doctor, De Castro retired from football on the spot in protest at the age of 26 and spent the rest of his working life practising medicine in Belo Horizonte, before dying aged 92 in 1998.

4) Peter Knowles

He was “God’s footballer”, or at least that’s what Billy Bragg called Peter Knowles: a supremely talented Wolverhampton Wanderers striker and England Under-23 international, who even had the temerity to turn down a move to Bill Shankly’s Liverpool. But after answering the door to two Jehovah’s Witnesses during a 1969-70 pre-season tournament in Kansas, USA, the 23-year-old returned to the Black Country a changed man. “I shall continue playing football for the time being but I have lost my ambition,” he said. “Though I shall still do my best on the field I need more time to learn about the bible and may give up football.” Wolves won their opening seven matches with Knowles in fine scoring form, but after they drew 3-3 with Nottingham Forest on 6 September 1969, Knowles walked away from the game, unable to reconcile his lifestyle – the MG sports car in his drive with his name on the side, a poor disciplinary record and the adulation he received from the terraces – with his newfound religious beliefs. “I thought to myself, this isn’t right, I’m just an ordinary person,” he said.

Facebook Twitter Pinterest Peter Knowles with his bride Jean at their 1967 wedding ceremony shortly before he quit football for religion. Photograph: David Bagnall/Rex/Shutterstock

Nobody took him very seriously: not a single team-mate said goodbye after that Forest match, believing he would soon come to – indeed the Wolves manager, Bill McGarry, had Knowles’s kit laid out for him at training as normal the following Monday. In fact, Wolves kept him on the books until 1982 in the hope that he would one day return, but he never did, instead working as a milkman, a window cleaner and in the warehouse of Marks and Spencer. In a rare interview, he insisted he had no regrets: “There hasn’t been one day in 40 years where I have turned around and said to myself, my wife or my friends, ‘I wish I hadn’t packed up football’. It’s the best decision that I’ve ever made. I’m content with life. When I look at my standard of living and how it has dropped over the years, it doesn’t matter. I have my health. I’m still married — and if I had carried on playing football I wouldn’t have been!”

5) Espen Baardsen

Football: Where are they now? Espen Baardsen Read more

Five years after retiring, Espen Baardsen described to the Observer in 2008 his final day in football: “I had been living out of hotels and suitcases for months. It was in a Tesco in Sheffield that I reached my lowest point. I went into Neil Warnock’s office to negotiate my wages and he offered me less than what a tube driver earns. I turned it down. I got bored of it. I felt unsatisfied intellectually, I wanted to travel the world.”

Of all the abandonments on this list, Baardsen’s seems the most pragmatic. He was a good goalkeeper, nothing more, who had gone to the World Cup in 1998 with Norway but played second fiddle at every club after, at Tottenham, Watford, Everton and Sheffield United. Just like 25-year-olds up and down the country, he was bored with his job, not making enough money and fancied a change. So he went travelling for a bit, got an Open University degree and got a gig in finance, managing “close to a billion dollars”, dealing in interest rate trades, foreign exchange rates and stocks. “You wouldn’t think a person working in the city could say this, but I’m more relaxed, five kilos lighter, fitter and healthier than I was at the end of my football career,” Baardsen added. “Football is stressful, try playing in front of 40,000 crazy football supporters who are happy or sad for their whole weekend depending on how you perform.”

Facebook Twitter Pinterest Espen Baardsen, pictured in 2008, where he worked as a macro analyst for Eclectica asset management. Photograph: Richard Saker for The Observer

6) Carlos Roa

If you genuinely believed that the world was on the verge of apocalypse, negotiating a new contract is probably not your top priority. Indeed, that was the case for 29-year-old Carlos Roa in the summer of 1999, the goateed Argentinian goalkeeper who had sent England tumbling out of the 1998 World Cup after saving David Batty’s penalty. After reaching the final of the Cup Winners’ Cup with Real Mallorca, Roa retired from football in order to join a religious retreat, part of the Seventh-day Adventist Church – and unfortunately for football – whose followers observe sabbath on Saturdays. “The year 2000 is going to be difficult,” Roa declared. “In the world, there is war, hunger, plague, much poverty, floods. I can assure you that those people who don’t have a spiritual connection with God and the type of life that he wants will be in trouble.” Y2K came and went without event, and Roa did eventually play football again, re-joining Mallorca on the proviso that he didn’t have to play on Saturdays. It didn’t work out.