The veteran goalkeeper says that he is not getting any younger and believes that it is now an opportune time for others to have a go at helping Ireland to a major tournament
The 36-year-old shot-stopper announced that he was retiring from international football ahead of Ireland's friendly game with Serbia and admits that it was a 'big decision'.
"It was a big decision and the biggest football decision you will ever make," he told the Irish Examiner.
"I have been thinking about it for a while, for weeks and months. And I just felt now was the right time to make the decision before the new [World Cup] campaign starts."
He added: "It’s time for someone else to try and qualify and now was the right time to step aside."
The Donegal born player said that he would like to commit himself to Aston Villa as he sees out the remainder of his career.
"I have four years left on my contract at Aston Villa and I felt that it was only proper that I give them everything I have."
He continued: "I am obviously not getting any younger and your body takes longer to recover when you are travelling with Ireland. There is no real break in the whole season and it does get tougher when you get older.
"It’s only a friendly but if you’re involved in that, it will be a case of getting back Wednesday night or Thursday morning, travelling through the night, and you’ll be a bit knackered on Thursday, a bit tired on Friday, and the Premier League season starts on Saturday.
"All these things add up over the course of a season," he said.