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Cooper, who has just started his first season with the Kintetsu Liners in Japan's second division rugby competition, spoke to former New Zealand Warriors player and friend Isaac John about his extensive and at times controversial rugby career.
Speaking about the incident which occurred in the lead-up to the 2011 Rugby World Cup, Cooper said he has since approached the former All Blacks captain and owned up to the "dirty" act.
"A few years later I've seen Richie in the airport and I went up to him and said, 'Sorry about that'," he told John on The Ice Project podcast.
"It's not that he didn't care or he did care but, when I said sorry to him, I confronted it and said, 'I really looked up to you as a kid, you were my idol, everyone in New Zealand loves you and I loved you, so when I played against you it was just emotion, passion took over, you were playing dirty on me and I kneed you.
"He's one of the best at [dirty play]."
The 70-test playmaker revealed he wasn't prepared for the backlash he faced from the country he had grown up in at the time.
"I look back at it now and I wasn't ready for it," Cooper said.
"I had the expectation of 2011 of playing good football but now I had the pressure of all these guys hating me as well, and a whole country, not just the rugby public. I couldn't go anywhere. I was on the team bus and there were signs 'I hope you break your leg, I hope you die in this game'.
"If I had my time again, [because] I know how to handle it now, I'd just say, 'Yeah I did it, so what?'. Not 'So what?', but 'It's part of footy, it was a bad play but I did it', so what could people say?"