Former Manchester United captain Keane was a former Republic of Ireland teammate with McAteer but the duo seldom saw eye-to-eye.
The hostilities stemmed from McAteer's criticism of Keane's decision to walk out on his country on the eve of the 2002 World Cup.
A few months later, the pair clashed during a Premier League match between United and McAteer's Sunderland.
Keane planted an elbow on his international teammate and was subsequently shown a red card for his actions.
Tensions simmered for a while before McAteer leaped to the defence of former Ireland star Jonathan Walters who came under fire from Keane for failing to win a trophy during his career and 'crying on TV about his family situation' during an interview with Off The Ball.
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Former Liverpool midfielder McAteer condemned Keane for his attack on Walters, claiming he had let himself down with his comments.
"We all know Roy, he says what he wants and that's why he's box office because he says it how he thinks," the former Liverpool midfielder told talkSPORT in 2019.
"It's very watchable at times, but unfortunately I do feel he lets himself down with the comments he makes about other players and I was disappointed that Roy came out and said some of the things he did.
"Jonny is a brilliant guy and he's an advocate for mental health. He's gone on telly and put himself out on a limb because he feels it's going to help people, and it is.
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"We need to create more awareness of mental health these days and what people go through, certainly elite sportspeople because it's a very demanding environment and unfortunately when you come out of it it leaves you with problems sometimes.
"Jonny feels the need to come out and help people, which is fantastic, you take your hat off to him for that. So for Roy to bring him down and suggest he needs to stop crying on the telly, it was a poor comment.
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"I think he got wrapped up in the environment, everyone was laughing, there was a lot of people in the audience and he maybe got a little bit too comfortable with his comments and he let himself down.
"As far as of the other comments between them, they are Roy's opinions and Jonny has come out and said what he needed to say about the situation, and it's just whose story you believe.
"Roy does like the medals one, but at the end of the day you can't take the medals down the pub and have a pint with them. They don't talk back to you. I'd rather have a couple of mates than a couple of medals, to be honest."
The pair have reignited their feud in recent days after Keane admitted his elbow on McAteer in 2002 was deliberate, claiming he didn't deserve to be sent off.
McAteer responded with an extravagant offer of a boxing match to settle their differences and even called on promoter Eddie Hearn to make it happen.