IT is Joe Schmidt against Vern Cotter, Goliath against Goliath, Heineken Cup champions against potential champions, the present against the future.
Leinster v Clermont Auvergne,
Aviva Stadium, Tomorrow 3.40
Live Sky Sports 1
Can Clermont set aside their rank bad luck away to Leinster and come up with what their captain Aurelien Rougerie calls "the solutions" tomorrow?
They definitely have the raw material: "They are a high-speed machine," said Schmidt.
More than that, they are one that has shown full commitment to the Heineken Cup, determined to follow in the footsteps of Toulouse as an outward-looking French club.
"I remember my first year in Clermont. We had a draw, 19-all at Munster, who went on to win the Heineken Cup, and when we went away to Munster we made 14 changes," recalled Schmidt of his time as assistant coach to Cotter.
"There was just no real interest in the Heineken Cup. It was all about winning the (French) Top 14. But, when the Bouclier de Brennus comes from your region and it hasn't been back there in over 100 years, there is a big-sized carrot.
"That did exist. That is now something they have achieved. I have never, ever been in a situation where I have seen Clermont rest a number of their top-flight players against Toulouse so that they can be better prepared against Leinster in the European Cup."
This is exactly what happened two weeks ago when Clermont almost snatched a losing bonus-point (30-22) away to Guy Noves' club in the south of France.
"That has to be the clearest indication of the swing that they have made. Aurelien Rougerie, I remember, before I left even, was outspoken and said, 'Look, we've reached the top in France, we've got to go to the top in Europe'.
"They are too cosmopolitan, too professional, too well-equipped now for any team to expect, if they can get ahead of them after 60 minutes, that they are going to fold, because I just can't see them doing that."
Still, the post-match words from Cotter about the victory over Leinster providing a "lift to the players' confidence" spoke of a lack of belief within Clermont.
The Leinster whole is beginning to look greater than the sum of its parts, something once said about Munster. They could have and should have taken a draw, at least, from the Massif Central. Scrum-half Morgan Parra wants to avoid a repeat of the 2010/2011 scenario when Leinster took a losing bonus point back from Stade Marcel Michelin and stuffed Clermont 24-8 at the Aviva Stadium.
"We've already had the chance to play this double-header and, after conceding a defensive bonus point at home, we went to Dublin with good intentions before exploding.
"We don't want to relive that experience. We'll need to show that we've made some progress," emphasised their 'Little General'.
There is an imperative that any shade of a win will extend Leinster's stay in the competition to Rounds Five and Six, where they will have to take two more wins at home to The Scarlets and away to Exeter Chiefs to qualify as one of two best runners-up.
It would be negligent of the front-row club not to go after Clermont at scrum time.
They could also do with greater reward from English referee Wayne Barnes than they did from Welshman Nigel Owens last Sunday.