Players who can switch allegiance to Ireland
Curtis Davies (Hull)
The 28-year-old defender has represented England at U-21 level and was named in senior squads without making an appearance.
O'Neill paid £9.5m to bring him to Aston Villa but Davies criticised the Derry native after his departure.
Kyle Naughton (Spurs)
The defender was courted in his youth by both Ireland and England and sided with the latter but fell short of a breakthrough at senior level. Giovanni Trapattoni mentioned the former England U-21 operator but never managed to make any progress.
Connor Wickham (Sunderland)
As a highly rated teenager at Ipswich, his then manager Roy Keane compared Wickham to Wayne Rooney.
They had their issues afterwards and he was sold to Sunderland where he worked under O'Neill while flattering to deceive. The 20-year-old has extensive underage experience with England.
Will Keane (Manchester United)
His brother Michael declared for England after playing youth football for Ireland. Will, who was always highly rated, stayed with the country of his birth.
"He's come back (from injury) and I watched him the other day and he went off injured after a minute," said Noel King. "But he's still a player with potential. Again, England would be his first port of call."
Patrick Bamford (Chelsea)
The physical attacker is making a good impact at MK Dons and is targeting a breakthrough at his parent club while humming and hawing over his international intentions.
As he has already played underage games for both countries, the rules say that Bamford's next move is final.
Ryan McLaughlin (Liverpool)
Liverpool right-back who is making waves at Anfield and refused a call from Michael O'Neill to join the Northern Ireland senior panel.
Prompted inevitable speculation that the Belfast lad will defect to the south, but assured the IFA that wasn't his plan. However, he has the freedom to go either way now.