Football manager Arsene Wenger has warned that if Britain votes in favour of leaving the EU it could raise serious questions for the Premier League.
The Arsenal boss told the Guardian he felt a Brexit would lead to uncertainty over which players would need permits in future.
He said: "It raises many questions. Will the European players be considered as they are now? For example, if England votes for Brexit, will the French be considered like South American players [who require work permits]?
"That would completely re-question the influx of foreign players."
Wenger's comments came as the EU referendum campaign officially began on Friday.
Boris Johnson has criticised Barack Obama who plans to urge the UK to remain in the EU referendum branding it "hypocritical".
The EU referendum campaign has officially begun - ten weeks before Britain decides whether to leave the union.