Now 36, O'Neil says he was wanted by former Reds manager Rafa Benitez.
"I got a phone call off an agent I didn't know saying 'If you don't let me do it or us do it then it's not going to happen'.
"I was like 'I've been with my guy for ages, it's all done'.
"I got a call off my agent a couple of days later saying they'd pulled it."
He continued: "I thought I was going there in the next window. I don't know how real it was, whether my agent was pretending how real it was, I was only young at the time.
"I have never heard of him (the agent) since. I'd only spoken to my agent when we had the terms sent and it was all agreed.
"I thought I was nowhere near good enough or ready for this but thought let's roll with it and get better when I get there."