Northern Ireland manager Michael O'Neill said the most upsetting aspect of international eligibility rules is the pressure on young players to make an irreversible choice. Any player born in Northern Ireland can also play for the Republic of Ireland, but Fifa rules allow only one transfer of allegiance. The case of Arsenal teenager Ceadach O'Neill has highlighted the issue: he has two senior caps and was named in the Nations League squad, but the Republic of Ireland has approached him. If he plays in the upcoming quadruple-header, he must wait until 21 to transfer; with four caps, he could never switch.

"My focus is on the player, and I have a duty of care," said O'Neill. "Putting a young player in a position to make an international transfer before he's been a professional for even two years is not the right thing."

Under the Good Friday Agreement, those born in Northern Ireland can hold both British and Irish passports. A 2010 Court of Arbitration for Sport ruling lets players born anywhere on the island represent the Republic. O'Neill noted the rule is unique between Northern Ireland and the FAI. "Everyone recognises it's not particularly fair," he said, stressing the focus remains on a strong pathway for young players.