Sky Sports News has uncovered a growing concern among officials at Premier League clubs that huge sums are leaking out of football when top players allow their contracts to run down and then sign for another club without a transfer fee being paid.
Official Football Association figures show that, for all transfers completed between February 2016 and January 2017, £219m was paid in agent fees across the Premier League and Championship - a rise of 38 per cent.
Sky Sports News has been told by a number of club chief executives that the expectation is that figure will rise even higher in the coming years.
None of Zlatan Ibrahimovic's move to Manchester United from Paris Saint-Germain in the summer of 2016, Paul Pogba's move from Manchester United to Juventus in 2012 as a 19-year-old or Sead Kolasinac's deal in June that saw him leave Schalke for Arsenal involved a transfer fee, but all of them involved huge up-front fees as part of the contract.
There is no suggestion that the player or his representatives did anything wrong, or outside the rules.
Tim Bailey, a Sports Lawyer at Beswicks Legal, told Sky Sports News "free transfers" can actually now prove very expensive, as he said: "There's no such thing as a free player. You get to a situation where you have a top-flight player, he gets to the end of his contract and you can then, to an extent, name your price.
"You are able to leverage much higher wages, and certainly as an intermediary leverage much higher fees. We've noticed a lot of transactions of late where players have come into clubs as "free" agents, but actually he is being paid a much higher salary than he would have got in a "normal" transfer where a club would be paying another club a fee for him."
For the buying club, because they don't have to pay a transfer fee, they are often happy to commit more on wages and signing-on fees and one executive at a Premier League club told me it feels "like you're paying a transfer fee to the agent, instead of another club; you know the money is leaking out of the game, but financially - it often makes sense."
He wouldn't speak on the record, for fear that it would highlight some of the out-of-contract deals his club has done, and also for fear that more top players will recognise it as a lucrative option.
Many more officials in football have concerns about this practice - which is perfectly legal, and within FA and FIFA rules - and Bailey is certain it is taking money out of the game, and into the pockets of wealthy agents.
He added: "I do believe that. I'm a big believer that money in the game should be used for the benefit of everyone in the game from the top down. And it's not right in my opinion that this is happening. We've seen the huge amounts now that are going straight out of the game to representatives."
Bailey says it's up to FIFA to act, but legally it is difficult to stop after the landmark Bosman ruling of 1995.
He also conceded while it can make good business sense for a top player, below Europe's top divisions, it is a risk for a player to run their contract down.
Bailey added: "That is always a gamble. The player could be injured, the club might get relegated, and his club can no longer offer him a contract, and his market value has gone down. So there is a big risk outside the top level.
"But if you're Ibrahimovic, there is always a club that will take you, and mostly pay him what he demands."