JOHNNY SEXTON V IHAIA WEST
This pair didn't get to face off last year as Sexton had been stood down due to head injury concerns. That he is back and in flying form tilts the balance in Leinster's favour today.
West is a stylish no 10 and scored the winning try against Racing in the semi-final but without his regular half-back partner, the injured Tawera Kerr-Barlow, the Kiwi won't have the consistently quick ball that Sexton will get from Jamison Gibson-Park, who is in red hot form.
Sexton, who turns 37 in July, is desperate to win a fifth crown and playing like it right now. His presence can make all the difference.
ANDREW PORTER V UINI ATONIO
It's easy to forget that Porter only made the move back from tighthead to loosehead last summer, when Leinster experimented with him there in pre-season fixtures.
It went well and he has progressed at pace, his switch turning the Blues' front row into one of Europe's most dynamic units.
There have been times when Porter has come under pressure and that will surely happen again in Marseille as he gives up over 30kg to his scrum rival, Uini Atonio.
Now 37, the Kiwi-born France tighthead is one of Europe's most fearsome scrummagers.
JOSH VAN DER FLIER V MATTHIAS HADDAD
On paper, this is a positive for Leinster in that experienced former All-Black Victor Vito is injured and his absence a real loss for La Rochelle.
Ronan O'Gara has gone with 21-year-old Haddad at no 7 instead, and he'll be up against perhaps Europe's in-form flanker in van der Flier.
Yet O'Gara lavished praise on the young Frenchman yesterday, pointing out how he played underage for France a year above his age grade, and has told him to go out and enjoy the occasion.
It could be a tough afternoon for him. Once upon a time van der Flier embraced a hard-working supporting role but is now among Leinster's dashing leading men, as underlined by his peers voting him as their Player of the Year last week.
The flanker has transformed his game, adding a dangerous ball carrying element to the industry that was always his calling card (along with that red scrum cap).
