United Kingdom's exit from the European Union could cause a "serious problem" with visa issues, UEFA president Aleksander Ceferin has warned, while suggesting Barcelona's Neymar and Lionel Messi could already face difficulties.
In November, Paris Saint-Germain's Serge Aurier was unable to face Arsenal in the Champions League after the player was denied entry to the UK because of his ongoing appeal against a "convertible" two-month prison sentence.
Ceferin, who also serves as a FIFA vice president, says that such issues could worsen after a "Brexit," and suggested that British teams could lose the ability to host European matches.
"If 'Brexit' happens, everything changes," Ceferin told The New York Times. "But football was played before, and it will be played in the future. Now, with free movement in the European Union, it is much better.
"I was very disappointed when Aurier, from PSG, was not allowed to enter England. That will worsen when Brexit happens, especially if the reasons were as formal. We could have a serious problem.
"If we see that players cannot enter because they have any sort of procedure ongoing, then we will simply think if we should play our European matches there."
The Champions League final is set to be played in Cardiff, Wales, in May, and Ceferin raised the possibility that Barcelona could be without superstars Neymar and Lionel Messi amid their recent trials.
Both Neymar and Messi played at Manchester City and Celtic in the Champions League in November without issue, though Neymar has since lost an appeal and will stand trial on corruption charges related to his transfer to Barcelona four years ago.
"Neymar and Lionel Messi both have procedures going on. This year, the Champions League final is in Cardiff. Imagine if they did not let them in," Ceferin said.
"That is a big thing for us, if players from England can travel anywhere but players from other teams cannot travel to England. With free movement in Europe, it is much better."
London's Wembley Stadium is also scheduled to host the semifinals and final of Euro 2020, and Ceferin said he hoped to avoid any issues.
"Even in 2020, if Brexit has happened, then it can be a big problem for fans," Ceferin said. "That stays firm, and we will speak to the British government, and I am sure the English Football Association will help us."
Ceferin also said that United States president Donald Trump's efforts to institute a travel ban would "not help" the nation's efforts to host the 2026 World Cup.