Roy Keane insists he should have retired instead of joining Celtic.
The Manchester United legend signed for the Hoops in 2005 after falling out with Sir Alex Ferguson and leaving Old Trafford.
He made just 10 appearances for the Parkhead side before retiring on medical advice.
And Keane admits he was not at his best during his time in Glasgow. He told Stick to Football: "I was 34 when I finished. But I should have retired when I left United. I even lost a bit of the love for the game after that.
"I went up to Celtic but my hip was really at me, painkillers for training. I tore my hamstring two or three times up at Celtic.
"I was commuting. I still had a year left on my contract and I rang Gordon. I went to see the hip specialist who said the longer you play on, the worse damage... he was talking about when I retire, about quality of life.
"I rang Gordon Strachan about what do I do. I had gone up there and kind of embarrassed myself, I wasn't really doing the business.
"I'd said I am finished but losing sleep before I rang him, as soon as I put the phone down I had closure on my career.
"I had no hesitation, I wouldn't say relief, but something lifted off me. When you have had injuries it beats you up."
