Sporting Lisbon president Bruno de Carvalho has told the BBC World Football Show that his club were under "big pressure" from third-party owners to sell Marcos Rojo to Manchester United this summer.
Argentina international Rojo eventually joined United for 16 million pounds in August, but only after the player had apologised to Sporting after refusing to train while the Portuguese club resolved their dispute with Rojo's management company Doyen Sports.
Sporting declared their contract with Doyen Sports "invalid" following the move, and FIFA has since voted to ban third-party ownership (TPO) of players -- a practise already banned in England -- which allows outside investors to profit from transfers.
De Carvalho says third-party owners attended meetings regarding the transfer, with Sporting officials believing that they were in fact representatives of Manchester United.
"We did not want Rojo to leave. He was an important player for us," he said. "The pressure was so big, they [the third-party owners] started to speak to the clubs and come here to the meetings.
"The directors thought they were people from the clubs because they were speaking in English although they were Portuguese. They believed it was a person from a club but it was a person from the funds."
The Premier League side told BBC Sport that it was an issue for De Carvalho and the third-party group, and had no further comment.
De Carvalho believes FIFA has made the correct decision in moving to ban third-party ownership, which has become a "monster" according to the Sporting president.
"We don't know where the money comes from. We don't know who are the people," he said. "The problem is we created a monster, a monster who started to come to football. Without regulations, they don't help the club. They only give them one, two, three years of surviving but after that they are dead.
"FIFA understand people all over the world don't want that menace in football. They are almost in every club right now. They are breeding all over the clubs.
"Clubs need solutions and there were people who came and said 'I have the solutions for all your problems', and they don't understand they are killing the game."
The Portuguese chief pointed to Radamel Falcao's loan move from Monaco to Manchester United and Eliaquim Mangala's 32 million-pound transfer move from Porto to Manchester City as evidence that third-party ownership favour richer clubs.
He added: "If you say the funds are very good for the little teams, let us see where are the players of the funds now? Falcao and Mangala -- where are they? In big clubs. So they are helping who? It's very simple to see they are not helping the little ones as they are still little. The big ones are bigger.
"People are very happy to sell a player for 50 million pounds, but for the club it is one million or two million. And they paid more than that in the salary of one year. Almost all the time you lose money. This is mathematics."