The 27-year-old has yet to make an impact on Villa's team after being held back by a calf injury but Cuellar is now fully fit and O'Neill believes he has the potential to become a regular member of Spain's squad.
O'Neill said: "Carlos' ambition is to play for Spain. He voiced that when he joined us. He thinks he's capable of doing it. Only time will tell whether he will.
"But I think he has the potential to do that. Carles Puyol has become a permanent fixture for Barcelona and Spain for years. I think Carlos feels, at 27, he has the time to do so.
"Carlos is a defender who has a little bit of ability. He can manoeuvre it. He also wants to come and head the ball. He is wiry more than anything else but is a real competitor.
"I saw a lot of his games in European football for Rangers. From last Christmas onwards we really started taking an interest in him."




