​Former Manchester City defender Nedum Onuoha says Kevin Keegan was an “incredible mentor” to him, having been handed his first-team debut by the Englishman after progressing through the club’s academy ranks.Keegan, who spent four years in charge of the Citizens between 2001 and 2005, has died weeks after revealing he had been diagnosed with stage four cancer.”It wasn’t just a debut for me because it was a life-changing moment,” Onuoha told BBC Radio Manchester. “I think back on all the work I had to put in before that to get the opportunity to do it, but he was the first coach that gave me the chance to even train with the first team.”Before I knew it, I went from being a ball boy at Maine Road, watching his teams, to being in and around some of those same faces. It was an incredible feeling. He believed in us academy players and he gave us the opportunities.”Whether it was just training with the first team, making it into the first team or starting peoples’ careers, he was very much invaluable in terms of the history of the football club.”He was an incredible mentor to me, I owe him so much. He came in and changed things, such as the mood at the training ground and the general belief of the club. It was evident there was something different about the football club when he came in. It was positive and hopeful.”Then, as if by magic, Manchester City were playing Barcelona at the City of Manchester Stadium under his stewardship. It was refreshing to see the club drifting towards a better direction again. It was surreal to be part of it.”Listen to the full conversation above or listen on BBC Sounds