Cullen's charges must now control destiny
Van der Flier has to stymie Armitage on European debut
Leo Cullen nailed it on the head when it comes to how to beat the unbeatables.
"I think you've got to be hugely respectful of the ball," he said.
"If you turn it over cheaply, they've so much pace and power that they will punish you from those unstructured situations."
As the Leinster coach trotted out those words, the memory came alive with that winner-take-all ball from Ian Madigan that was seized on by predator par excellence Bryan Habana to seal the semi-final last season.
It encapsulated in one action what Leinster cannot do in the south of France.
They have to play a calculated risk-reward strategy based around keeping the ball without getting too greedy for the big lights-out play.
There are few better at that particular skill than Jonathan Sexton. He will team up with Isaac Boss at half-back where game-management is going to have to be right out of the top drawer.
Leinster have their own virtuosos who seem to turn up when they are most in need.
Rob Kearney is short on game time, long on big game experience.
Isa Nacewa, Fergus McFadden and Luke Fitzgerald in the three-quarters can all prosper, while Ben Te'o could give them the front-foot.
Mike Ross's reign at tight-head continues and Cian Healy has to show he is ready and able to produce something close to his best.
The set-piece solidity of Richardt Strauss is preferred to the explosive nature of Seán Cronin.
The second row is well-balanced in terms of the lineout nous of Devin Toner and the naked aggression of Mike McCarthy.
Rhys Ruddock can compete with anyone in hand-to-hand combat.
Jamie Heaslip is an anchor at the back of the scrum and a cool head in a storm.
And then there is Josh van der Flier's assignment to beat Steffon Armitage to the space at the first breakdown.
"It's his accuracy in terms of arrival at the breakdown when we're in possession, so it's that ball security where the seven is generally the first guy at the breakdown. He's a guy who offers a lot in that area."
It is the closest thing you will get to a man-marking job off first phase ball, from scrum, from lineout.
After that, the policing of Armitage broadens out become everyone's problem.
The no excuse policy does not guard against how daunting a mission Cullen's charges face into.
But, Leinster's leader has seen it all before.
"I almost feel it was more daunting going back ten or 15 years ago because of the sense of going into the unknown when you went away for those French trips.
"I remember going to Toulouse before. That felt more daunting," he remarked.
Maybe, that is because he no longer has to cross the white line for work.
Devising the game-plan is a world away from carrying it out when there are so many dangers lurking in the short grass at Mayol.
"Of course, it's daunting because they've got big names of world rugby.
"But, there is a certain sense of familiarity. We've played against all these guys before. We've played in Stade Felix Mayol as well."
The direction in which the game is going is scary.
The financial muscle of the French and English clubs could just take the Irish provinces out of the genuine list of contenders.
The instant fix of importing world class talent, like Ma'a Nonu, Samu Manoa and Duane Vermeulen, is countered by the slow drip feed from the Leinster Academy.
"We want to be the best team in Europe," said Cullen.
"We want to pit ourselves against the best. For the last three years, Toulon have been that team.
"Previous to that, we were pretty close to being that ourselves. We've just been working hard over the last couple of years to try and get back there."
This is the best place to start.
Toulon: D Armitage; B Habana, M Bastareaud, M Nonu, D Mitchell; M Giteau, E Escande; F Fresia, G Guirado, M Stevens, S Manoa, R Taofifenua, M Gorgodze, S Armitage, D Vermeulen.
Leinster: R Kearney; F McFadden, B Te'o, L Fitzgerald, I Nacewa (capt); J Sexton I Boss; C Healy, R Strauss, M Ross, D Toner, M McCarthy, R Ruddock, J van der Flier, J Heaslip.
Toulon v Leinster, Stade Felix Mayol, tomorrow ko 3.15 (Sky Sports 3)