A leading sports immigration lawyer has warned some European players may no longer be able to play in the Premier League if Britain votes to leave the European Union next week.
Currently players from countries within the EU can work in Britain without a work permit but that could change if 'Leave' prevails in the Referendum on June 23, although it is likely to be several years before the effects are felt.
Last season 432 European players were registered to play in the Premier League. Those players are unlikely to have to leave but should the vote go against 'Remain' new players would not have an automatic right to live and work in the UK.
The Home Office could roll out current immigration rules for non-EU players for Europeans under which a player from a top-10 nation only has to have played in 30 per cent of their games in the two years prior to the date of application to be granted a work permit.
A player from a nation ranked 11-20 must have played in 45 per cent of international games and that percentage rises to 60 per cent for the next 10 countries, then 75 per cent for nations ranked 31-50.
A vote to leave the EU would mean that players from the 27 countries still in the union would need to meet these criteria.
That would mean top Premier League players of the calibre of French duo Dimitri Payet of West Ham and Leicester's N'Golo Kante would fall short of the criteria required having not figured regularly for their country.
The Bosman Rule, where a player can leave his club for free at the end of his contract, would not change as the rule is encapsulated under FIFA and domestic rules and not reliant on European law.
Speaking to Sky Sports News HQ, leading sports immigration lawyer Maria Patsalos said: "A good example at the moment is Dimitri Payet and N'Golo Kante, two fantastic French players who have lit up the Premier League this season.
"They have not been playing for their French national sides regularly at all. They would not have been given the opportunity to play in the Premier League if we are talking in three or four years' time.
"It would be a massive loss. Obviously Payet has done an amazing job at West Ham and Kante, who knows if Leicester would have won the Premier League title without him? We would see an issue with the younger, not so developed players coming through and being given the opportunity.
"There could be a catastrophic effect. We don't know for sure".
However, others have claimed the restriction on foreign players could nurture homegrown talent and be better for Britain in the long run.
Barry Hearn, chairman of Matchroom Sport said: "We won't lose anything from the top end at all as we pay the most money.
"Simply put, what we will potentially lose is middle range cheaper options not being able to come in so easily which I think is a good thing as it gives our own kids a chance to fulfil their dreams."
Retired footballer Vinnie Jones said: "What I did say 20 years ago was if it becomes a European Premier League, the national team was going to struggle.
"That was always going to be the price that we paid for flooding it with European players. Now I'm not saying that is wrong as the football is fantastic to watch, but a bit like me, the old tackles have gone."
Other areas which may suffer from a 'Leave' vote next Thursday could be the lower leagues of some smaller sports, added Patsalos.
"Where it is difficult already it's going to be even more difficult," she said. "Currently the lower leagues find it difficult to bring in players who are well established internationals and meet our current UK immigration rules.
"So if those rules are expanded to European nationals they are going to find it even harder to bring in those players as well and the same goes for other sports.
"If you don't have well established international sports people they don't meet the current UK rules and they won't be able to bring them in."