Keegan, who turns 70 today, was City manager between 2001-05, a period that saw us win promotion into the Premier League in wonderful fashion before consolidating ourselves in the top flight after years of yo-yoing.
It was a memorable phase in the Club’s history, with Keegan raising expectations and drastically improving the quality in our squad.
He gave Onuoha his debut and the former City defender says Keegan was the first manager to encourage him to adopt a modern, ball-playing game.
“He truly was special,” Onuoha said on our We’re Not Really Here live matchday show.
“He provided me with my debut. I was 17 and he wanted to get me in his team. He knew I wasn’t going to displace Sylvain Distin or Richard Dunne. I had to work on areas of my game.
“But he still trusted me to go into the side and played me at right-back next to those two. He said: 'You should learn from these two.'
“He made such a great effort with everyone in that team. We had lads coming through from the academy and he was great with them. And, as I say, he was great with me.
“There is one specific story I remember. We were playing a pre-season game, I was playing centre-back, the ball went down the channel and I raced over to get it.
“I had an attacker on my back and I just rolled the ball out of play, they had a throw and we played on.
“After the game he came over to me and said: ‘Come on, son. I want the best for you. In those moments, I want you to get the ball and roll it to the ‘keeper who will then start the next attack.’ He was the first manager to say that.
“City’s academy at the time didn’t have a complete ball-playing philosophy. He showed me the importance of demonstrating personality and character on the field – trying to do things the right way.
“That story is from 17 years ago but I remember thinking: 'Kevin Keegan’s just told me something about how he thinks I’m a really good player and I could do this and become even better.' He gave me the chance and here I am years later.”
City’s focus under Keegan was very much on attack, often employing two playmakers and two strikers in the same side.
The 2001-02 season saw us score 108 league goals as Keegan guided us back into the Premier League at the first time of asking.
And the following season we signed Nicolas Anelka and Peter Schmeichel, finishing ninth and qualifying for Europe under fair play rules.
Perhaps the standout match of the Keegan era was the FA Cup classic against Tottenham Hotspur at White Hart Lane in 2004 when City came back from 3-0 down to win 4-3, despite being down to ten men.
Onuoha describes working with Keegan as 'an honour' and says being involved in a side with such dedication to attack was the best possible environment for a young player learning his trade.
“I feel really honoured to have been managed by him,” he said.
“The style of play he implemented – when we came up from the Championship and then we were in the Premier League under him – that’s not normal. It was a really blessing to see that.
“For me, having been a supporter and seeing it and then having the chance to play in that system, I am so lucky.”