GLASGOW, Scotland (AP) _ Former Manchester United captain Roy Keane retired from competitive soccer Monday because of nagging injuries that have plagued him the last year.

The 34-year-old Irish midfielder, who played with Celtic this season, said he was quitting based on medical advice from his surgeon and Celtic doctor.

``I feel my only option is to retire,'' Keane said in a statement on the Celtic website.

A lingering hip injury got the better of Keane, who had said he would make a decision on his future after speaking to team physicians this summer.

``Roy Keane is one of the greatest ever players to grace the game of football,'' Celtic manager Gordon Strachan said. ``It was fantastic that we were able to bring him to Celtic and it has been a privilege to work with him.''

Irish Prime Minister Bertie Ahern also paid tribute to Keane.

``Today is a sad day for his legion of Irish fans, his immense footballing genius is unlikely to ever be forgotten,'' Ahern said. ``Roy Keane is one of the most decorated Irish players of all time. Over the past decade, he has been arguably the greatest midfield player in world football and has established a reputation as one of the true legends of world football.''