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The arrivals to Manchester of Eliaquim Mangala and Marcos Rojo have brought Doyen Sports firmly into the English spotlight. Each deal was protracted by the funding group’s involvement as the Premier League sought guarantees over the ownership of the players’ economic rights. But just who are Doyen Sports and what do they do?

Doyen Sports is an investment fund supported by a collection of wealthy – and anonymous – businessmen speculating on the purchase of footballers to make money.

Instead of buying up players’ economic rights, as with other third-party ownership schemes, Doyen loan money to clubs to assist in transfers of notable targets who would otherwise be unaffordable.

Welcome along: Marcos Rojo was unveiled at Manchester United following his £16million transfer from Sporting Lisbon

When a player is sold a percentage hitherto agreed is returned, meaning Doyen reap a share of any profit. Alternatively repayments of initial loans are expected within three years at a set interest rate – as with any lending bank – but in general there remains an impetus for transfers to be made.

On their website it reads: ‘Our partners include some of the world’s pre-eminent law firms, financial advisors, sports consultants and football agents, giving the company and its clients confidence and protection in the investment decisions.’

Who is behind the scheme?

Nelio Lucas, a 35-year-old Portuguese entrepreneur, is the chief executive and main face of Doyen Sports. About four years ago he approached two wealthy businessmen and proposed his idea for enjoying football and making a profit from it – thus beginning the company.

Lucas is said to have learned his trade under Pini Zahavi, the super-agent involved in bringing Roman Abramovich to Chelsea, and has close relationships with many of the game’s biggest boardroom figures, including Florentino Perez, Real Madrid’s larger-than-life president.

New signing: But France defender Eliaquim Mangala is yet to make his debut for Manchester City

‘The money is only one part, the most important part is the networking,’ Lucas said in an interview with Bloomberg from May. ‘I know all the sports directors, all the presidents. They’re my friends for so many years. There’s a friendship situation in order to negotiate.’

Jorge Mendes, the agent of Jose Mourinho and Cristiano Ronaldo, and Peter Kenyon, former Manchester United and Chelsea chief executive, have been incorrectly linked to Doyen. Their vehicle is a third-party ownership model called Quality Sports.

In April last year Doyen Global was launched to manage the commercial aspect of elite footballers, including Neymar. It is run by managing directors Simon Oliviera, a key strategist in David Beckham’s team for 10 years, and Matthew Kay, who has managed the images of Mourinho and Ronaldo among others.

Not him: Jorge Mendes, the agent of Jose Mourinho (pictured), has been incorrectly linked to Doyen

How much money are we talking and which players are involved?

So far €100million (about £80m) has been invested in players, with another €100m on the way. Lucas says the sums are ‘drops in the ocean’ for the group’s multi-millionaire backers.

One of the company’s biggest and earliest transactions was in 2011, when Radamel Falcao switched from Porto to Atletico Madrid for £34.7m, even though the Spanish club was in deep debt. Last summer he moved to Monaco for £51m and is on the market again this window, although Doyen’s interest in his transfer ended when Monaco bought in full.

Doyen claimed a third of Mangala’s transfer to Manchester City, having assisted Porto with his move in 2011, and are owed 75 per cent of Rojo’s transfer although a dispute with Sporting has broken out and no money has been handed over to date.

On Doyen’s website names such as Alvaro Negredo, Alvaro Morata, Steven Defour and Jose Antonio Reyes are listed but it is not stated in what capacity they are linked.

Subject: On Doyen’s website Real Madrid's Alvaro Morata (right) is listed but it is not stated in what capacity

Atletico Madrid have a wide-ranging financial agreement with Doyen that allows them to buy players they could otherwise not afford.

‘We are sharing the risk,’ Atletico chief executive Miguel Angel Gil says. ‘It’s an interesting transaction because if the player doesn’t do well the club doesn’t lose everything.’

Recently Doyen has announced an agreement with FC Twente and that it financed Porto’s deal for Algeria World Cup star Yacine Brahimi from Granada.

What is the global reception to Doyen?

Spain’s top-flight is very welcoming, with La Liga president Javier Tebas arguing Doyen offer the funds to provide smaller clubs the chance to compete when Real and Barcelona hog the TV money. Spanish football clubs have a combined tax debt of £550m.

But the Premier League is extremely sceptical and would not allow Doyen to finance any deals entered into by clubs in England’s top division. Third-party ownership was outlawed after the Carlos Tevez and Javier Mascherano affair and even though Doyen state firmly their model is different and does not exert influence on clubs, the Premier League remain wary.

They have concerns relating to funding schemes imposing penalties for non-sale of players. Doyen insist they do not employ such measures.

Rule: Third-party ownership was outlawed after the Carlos Tevez and Javier Mascherano affair

A Premier League spokesman told Sportsmail: ‘Premier League rules prohibit Third Party Ownership as we believe that it threatens the integrity of competitions, reduces the flow of transfer revenue contained within the game, and has the potential to exert external influences on players’ transfer decisions.

‘When our clubs enter into negotiations to sign players from countries where the practice is permitted we work with them to make sure any third parties are bought out. This has to take place before a player can be registered to play in the Premier League.’

A row between Sporting’s new president Bruno de Carvalho and Doyen broke out when he claimed the club were being put under pressure to sell Rojo to United. Doyen insisted this was not the case and could take Sporting to court for their refusal to hand over any money.

UEFA want to ban the practice, while FIFA have conducted various studies into its feasibility. Doyen are keen to distance themselves from other third-party entities and would welcome tighter regulations.