He was 23 and feared stagnating in a dressing-room dominated by old soldiers with strong personalities. O'Callaghan, essentially, coveted the No 4 shirt worn by Mick Galwey, a man then in his mid-30s, but still utterly committed to the Munster cause.
He decided to phone Wasps coach, Warren Gatland, having been made aware that the former Ireland boss was an admirer. Their conversation didn't dip into any specifics beyond Gatland assuring O'Callaghan that he would be given game-time if a transfer to London happened to materialise.
The tipping point for his decision not to move would be the news that Declan Kidney was stepping down as Munster coach to become assistant to Eddie O'Sullivan with Ireland. Before the end of the season, Kidney's replacement -- Alan Gaffney -- agreed to meet O'Callaghan in a Cork hotel.
On hearing his story, Gaffney re-assured the Corkman that his team selections would be based on form, not reputation.
"I thought if I spent another season rotting on the bench, other teams might not want to sign me," O'Callaghan recalled last year in his autobiography, 'Joking Apart'. "After a while, you become damaged goods."
It remains a moot point whether Kidney had yet to be convinced of O'Callaghan's worth or if his team selections simply reflected loyalty to the province's most revered figures. Galwey, particularly, had a status in the Munster dressing-room that transcended the mechanics of the game.
In the white heat of European competition, his voice often proved the whetstone for big, emotional performances.
For a coach, the hard-nosed, grizzled veteran can be a refuge of sorts. The professional game doesn't really facilitate any kind of induction phase for young talent into the sometimes jarring realities of Heineken Cup rugby. Youth becomes the coach's gamble.
And to gamble in Europe is to play a game of 'dare' with your own future.
For Rob Penney, any temptation experienced this week will probably have receded as the days progressed. He knows the importance of tomorrow's game at Stade de France to Munster's Pool One campaign and will, accordingly, have desired access to a starting XV that pretty much does what it says on the tin.
Penney may be expanding the breadth of Munster's play, but -- for now -- he will look to do so with certain qualifications. Hence the decision to give Paul O'Connell his first start of the season.
So, the experience of O'Callaghan 11 years ago is replicated for some of those who have made eye-catching contributions in the Pro12.
True, loosehead prop David Kilcoyne and openside Sean Dougall, get starts in Paris, but hooker Mike Sherry and back-row forward Dave O'Callaghan will have been prepared for disappointment at Penney's team announcement.
Kilcoyne lines out at No 1 because of an injury to Wian du Preez, but Dougall's third competitive start of the season confirms the brewing sense that Munster may have snared a gem from the Rotherham Titans.
The Scottish-born flanker essentially lost two seasons of his career with Leeds Carnegie to a shoulder injury, but won all the 'Player of the Year' gongs at Rotherham last season and, despite a sin-binning at Ravenhill, he has made a huge impression on the Munster staff this campaign as Niall Ronan continues the journey back to full fitness.
That said, Dougall lists Richie McCaw, David Pocock and David Wallace as his rugby idols and, but for the latter's recent retirement, it is debatable if he would have gotten the game-time Penney has afforded him in Munster's nine outings (three friendlies) to date.
Likewise, only the injury-enforced departures of Jerry Flannery and Denis Leamy facilitated the new coach in getting early-season access to Sherry and Dave O'Callaghan respectively.
Kilcoyne is regarded as one of those exotic rarities in Irish rugby, a talented young, home-grown prop, who could, if opportunity allows, be a future senior Irish international.
He was a stand-out performer for the Munster 'A' team that won last season's British and Irish Cup and any of those who witnessed his shuddering hit on the multi-capped All Black, John Afoa, on his first start of the season in Ravenhill recently will understand the excitement brewing in Limerick.
Kilcoyne is also a product of O'Connell's old Alma Mater, Ard Scoil Ris, and a winner of two All-Ireland U-20 titles with UL Bohemian.
Still, for Penney, the decision to toss a 23-year-old greenhorn in from the start against a monstrous Racing Metro pack is one that will seem viable only in the context of an emergency. And therein rests one of Irish rugby's eternal bugbears.
Because Kilcoyne was penalised on numerous occasions (unfairly in Penney's estimation) by referee, Leighton Hodges, during last week's Pro12 defeat to Leinster, the implication being that he was unable to cope with the nous and technique of Mike Ross.
Keith Wood believes that the Limerick man and fellow Munster prop, Stephen Archer (24), have "huge potential," but suggests that -- barring injury crises -- Penney may not have the luxury of time in which to explore to it.
"It's that difficult, catch-22 situation," Wood explained this week. "You need your scrum to be locked down, but you also need succession planning and to be able to bring these players through. And the two aims are rarely compatible. So it becomes a huge balancing act, trying to get these guys game time. It's one of the big issues I think for rugby, in that the only way to get guys technically up to speed is actually to get them almost humiliated in matches, hoping that they learn from the experience.
"But it's very hard to do that in Heineken Cup or even in a Pro12 game. There's a big match every weekend of the year now, so it becomes very, very difficult for the guys who aren't in the first 15 or the first 22.
"I'd like to see them playing a lot more rugby because, with front-row forwards, you learn from wily old fellas basically screwing you into the bloody dirt. We're not getting a huge amount of guys fully up to speed in that sense. It's why the 'A' games become incredibly important."
Leinster did manage the process well with Cian Healy, essentially accepting the reality that he would endure days in his education when both individual and -- as a consequence -- team suffered. Healy is now acknowledged as a world class prop. But he had to learn in the ring, not on the gym floor.
The men who maybe most compellingly represent the changing face of Munster just now are scrum-half Conor Murray, wing/centre Simon Zebo and immense No 8 Peter O'Mahony.
Then there is the palpable pressure being exerted by Ian Keatley on one of the province's institutions at out-half.
Ronan O'Gara is ten years older than Keatley and, according to myth, now being asked to re-invent himself for Penney's revolution.
It is surely the quaintest notion that a man who has held that No 10 jersey for 15 years, who is the record points scorer in Heineken Cup rugby and has won a Grand Slam and the Triple Crown three times with his country, might be somehow incapable of carrying a threat with ball in hand.
The rugby Penney wants Munster to play isn't exactly light years removed from the rugby Ireland played in the mid-noughties when, with O'Gara as fulcrum, the Triple Crown was won in '04, '06 and '07.
During that period, Ireland particularly targeted a bludgeoning England side by flooding the outside channels with bodies.
For four seasons in a row, England were beaten -- essentially -- by the breadth of Ireland's play.
That style wasn't an issue for O'Gara then and, logically, shouldn't be one now.
However, Keatley's form has, suddenly, given pundits cause to fixate on the Corkman's age.
The injury to Keith Earls perhaps allows Penney sidestep that issue this weekend with the former Connacht pivot chosen at full-back tomorrow.
But Wood agrees that O'Gara is "under pressure because Keatley is playing very well."
He expanded: "For a lot of Rog's career, there wasn't a viable alternative (in Munster). There is now. So Rog has to up his game to play.
"A point to remember though is that Munster might want to play a more expansive game, but they still want to play Heineken Cup style rugby too and it's a style that Rog knows incredibly well.
"So, while they looked really good at the start of the season, they were just getting that little bit more space because you're not playing the better teams.
"That's changed in the last two games (Ospreys and Leinster) and Rog has been put under an awful lot of pressure.
"He has to deal with that and I think you'd be a very brave man to suggest he won't be able.
"That said, Keatley has been playing a lot of rugby, looks in good nick and the style of play probably suits him.
"So, if Rog doesn't step up to the mark, there's a big, wide opening for Keatley.
"But I wouldn't be too voiciferous shouting the odds just yet, because a lot of people have come close to the mark in Rog's career and, yet, he has continued to deliver on big days."
Munster's young guns may well be making a loud noise then with Keatley (25), Zebo (22), Murray (23), Kilcoyne (23), Dougall (22) and O'Mahony (23) all starting tomorrow in Paris. Between them, Doug Howlett, Casey Laulala, James Downey, O'Gara, BJ Botha and O'Connell have an average age of 32.
The red revolution might be underway, but the old generals remain in charge.