Clermont coach Vern Cotter may have been "trembling" following Sunday's gripping three-point win against their familiar foes, but a message has already been conveyed to him that nothing may compare to the "cauldron" that awaits in Dublin this Saturday.
Their bloodied but unbowed squad will require the throaty roars of every man, woman and child to ensure their qualification hopes are not over before the final round of pool games.
Colloquially, the fiery but friendly local supporters in Auvergne bullishly declared that some 3,000 of their yellow-clad number would travel to Dublin this week; Leinster confirm that they have only sold the nominal allocation of 1,000.
Nonetheless, the 700 or so Leinster fans who witnessed the raucous, utterly uninhibited manner in which Clermont were backed by their passionate fans will have been put on alert for the return this weekend.
"The atmosphere was unbelievable," reported Isaac Boss of the scenes in the Stade Marcel Michelin, when the former French champions boasted their greatest attendance of all time.
"Clermont have great supporters and they really got behind the team. I suppose that's one thing they have in common with our fans. Hopefully our fans can get the place rocking next week. Hopefully, it's going to be a cauldron for us."
The relegation of Boss to the bench may constitute one or two of the necessary change-ups that Joe Schmidt must introduce in order to ensure that his ally turned adversary, Cotter, remains on his toes. Boss will form an integral component of the finished product, though, one he hopes can provide them with the win they so desperately require.
As the squad rested wearied bones yesterday, the erosion of mental scars will be just as crucial.
"We're confident because we were so competitive on Sunday," Boss insists. "We knew that to start with. We had no doubts. We had a belief that we could come over here and win.
"That's why we're so disappointed. We always have that confidence. But ultimately they're in the driving seat.
"We are mentally confident, though. We're physically battered and bruised, but next week can't come quickly enough. That always happens when you lose, you want to get out at them again.
"The hardest thing is putting everything into a game and losing, it's a really empty feeling. At the end of the day, we lost. And we didn't come here to lose.
"We came here to get four points at least and we truly believed that we could. But we have got to move on quickly, we can't dwell on it too much because there's a job to be done next week."
Cotter (pictured) was intrigued, but hardly surprised, at the wide variant of attacking gambits unleashed by Schmidt, featuring a number of delightful switch moves that threatened a decisive breakthrough on Sunday.
Yet Leinster have still managed to score just one try from their three European appearances this term; in contrast, their defensive record is immense; they have just conceded once.
This time two years ago, Leinster were never in contention to win in Clermont but escaped with a bonus point nonetheless.
Much more impressive was the manner in which they ruthlessly extinguished the French challenge in the return a week later, the beginning of the 17-game unbeaten run which propelled them towards two Heineken Cup titles.
Cotter is forewarned. "It's a tight one," he admits, despite the seemingly yawning five-point gap that separates the rivals.
"The biggest mistake is to think there's only Leinster in the pool. There's two other games too.
"These back-to-back confrontations determine the outcome most of the time. But this is going to be open.
"There's very few games that are as intense as that from start to finish. It was relentless from start to finish, especially at ruck time.
"They threw a lot of variations into their attack, and I thought we countered them pretty well. It'll be interesting to see what they come up with next week. Hopefully we get better."
That's what makes this contest so fascinating; each side trying to outwit the other. The game of chess transposed with shuddering violence onto a green sward.
"We'll try to come at them a bit harder," adds Boss, as if Sunday's effort was somehow undercooked.
"We're happy with the way we defended; we just need to be a bit more accurate on attack, take it an extra phase or two and capitalise on the opportunities that we create.
"It seemed like were doing 90pc of the work right and then it falls apart in one or two plays, with a pass dropping or a poor carry, just when it looked like they might be conceding a penalty, so we need to keep up the phases.
"We're gutted. It's hard to be upbeat about a few things. We need to move on quickly, it's only a six-day turnaround.
"But we could have easily come away with nothing. Something's better than nothing."
And so, like two heavyweight boxers, these formidably impressive sides will joust once more. Seconds away.