Leinster v Munster, Guinness Pro14 Championship SF: RDS, Saturday, 3.15pm
Two months ago he'd watched many of the same faces hoist silverware above their heads but it didn't bother him then at all, he wallowed in it.
A Grand Slam was the pinnacle for an Irishman and there were still more ambitions to achieve and trophies to chase.
Saturday was different though, as Peter O'Mahony watched Dan Leavy, James Ryan, Garry Ringrose and Devin Toner and all the rest gambol around their field of dreams in Bilbao.
Because on Saturday, although O'Mahony may be a proud Irishman, and he may have been happy for his colleagues, the sight of so many friends parading their wares pinched his soul a tad. So near, yet so far.
Not only another year without regaining their title but the knowledge now that Leinster will have a fourth star etched upon their chest, twice as many as the original trail-blazers in red.
"It was 100 per cent deserved," said the Munster captain, his admiration entirely heartfelt; as will be his intent on shaking up the four-time European winners this weekend in the RDS.
Rampant talk of new blue dynasties and such like pervading the air can only help to turn the air, well, blue down Munster way.
At least they are the first side to test their mettle against the standard-bearers; motivation enough to be playing Leinster in a PRO14 semi-final but also a Leinster side whose name will all week, and for several months, be prefixed by the words European champions.
"I'd be lying if I said I wasn't excited about having a cut off them, and of course it's a massive challenge," he said.
"We're the first up. We'll get the first opportunity. That's something that comes with being the champions. Everyone's jealous and wants to be like you.
"And every club in Europe now wants to be like Leinster, wants to be where Leinster are. They've been the best team in Europe and it's deserved that they've won, but what comes with it is every team wants to knock you. We get the first chance.
"It's got to be a challenge. If you're sitting at home worrying about going somewhere at the weekend, you're in the wrong business.
"You've got to see it as a challenge. Leinster are the team you want to be measuring yourself against. It's going to be hard, probably the hardest game we have played all year, but it has to be our best performance."
As much as it might rile them internally, the excessive chatter about the apparent yawning gap between the two provinces - even though Munster trumped their progress last season - could also salt wounds.
O'Mahony concedes such talk could be a distraction were it not for the fact they have enough to be worrying about.
"That's not what we're going to be talking about, certainly not us," he stressed. "We've a game plan, we've a structure, we'll go out and play it. We'll be talking about our performance and what we have to do to win. I don't want people saying after the weekend, 'Ah, Munster to be fair aren't far off Leinster'.
"If we play well, I want people saying, 'Munster played well', that's what I want to hear.
"What Leinster have done for the last 12-18 months, we're not going to change that in a game. That's the standard they have. We've got to strive to get there."
There could be annoyance too; after all, Leinster admitted to envy when the shoe was on the other foot a decade ago. Perhaps it's how you distil the hurt.
In any event, he observes the right for others to infer constant comparison between the two rivals.
"I don't think it's unfair," he reasoned. "Of course, you're going to compare provinces and critics are going to compare players and teams. That's part of it.
"It's not what we do. But we want to go out and perform, do as best we can. It's not about being ranked or anything like that."
O'Mahony accepts the difficulty of a side needing to back up such an intensive occasion with another merely days later on a physical and emotional level.
A tentative parallel with 2011's grand final in Thomond Park could be drawn - ironically the last time Munster won a trophy - when Joe Schmidt's comeback kings from the Cardiff final against Northampton were stung.
Yet, in rugby terms at least, that is a lifetime ago.
"It's a different game. That was seven years ago. You're dealing with the ultimate professionals on both sides," he said.
"It's just gone so intense now. You miss a beat and you've conceded a try or if you get pulled off tasks there is going to be a hole somewhere or maybe you've missed a jump.
"I think that's (sledging) nearly gone out of rugby. There's always going to be the odd one or two here or there but generally a lot of that has gone."
And so Munster's most important statement will be to deliver a performance; the only words necessary those between themselves as they attempt to navigate a route that Europe's best found impossible to breach.
"They have guys who are leading the way, as do we. You're going to get the best of Leinster at the weekend and they'll show that's their standard," he said.
"It's a semi-final. They'll be ready to go, whatever it takes."
It is for O'Mahony and his side to discover if they can summon what they need to stop them.