O'Shea was has been a club and international team-mate of Keane's; the duo played together at Manchester United from 1999-2005, during which time they won the Premier League and FA Cup together.
In total, O'Shea – now 37 – was a United player for 12 years until leaving for Sunderland in 2011.
And as the veteran defender prepares to retire from international football after his farewell match against the USA on Saturday - his 118th cap for the Republic of Ireland - Keane has joked how O'Shea was able to navigate through his career trouble-free, while praising his mental strength.
The Republic of Ireland assistant told reporters: "I remember him as a young player at United and thinking ‘this kid’s got a chance’ - decent player.
"Strangely enough, he always seemed really balanced. We’ve talked about all the pitfalls in football, but John always seemed to be really switched on.
"But listen, he could be a raving lunatic when he’s at home in the evenings – I hope he is.
"I hope he’s a head-case and we’re all proved wrong when he’s locked up in six months and we’re all saying ‘Jesus, I never saw that coming'.
"No, but I don’t think so. He’ll probably have a nice steady life, probably become a coach or a pundit."
Fine praise, indeed.
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