Former Manchester City and England right-back Danny Mills announced his retirement from football with immediate effect on Friday night.
The 32-year-old suffered a knee injury over a year ago and has been told it will not recover sufficiently to allow him to resume his career.
"Unfortunately I have now got to the situation where I can no longer continue to play," he told BBC Radio Five Live. "So, really as from today, I'll be retiring from the professional game and looking to do other things."
He added: "It has been difficult. I was fortunate it wasn't my decision in the end.
"I've been around the world - America, Germany, Sweden, London - I've been everywhere trying to get it sorted.
"I've been out for 18 months. I'm likely to have another operation in three or four months' time.
"Basically the knee just can't cope with it any more."
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