Leinster's Rhys one to believe
Captain Ruddock calls on Blues to make a big physical statement against French
All of a sudden, Leinster's strength in depth will be tested like never before.
Head coach Leo Cullen is missing Jonathan Sexton (knee), Robbie Henshaw (hamstring), James Lowe (suspension) and Rob Kearney (quad) from a first-choice backline.
The influence of half-backs Luke McGrath and Ross Byrne and centre Garry Ringrose will be paramount in the RDS this lunchtime.
Up front, Dan Leavy can't seem to catch a break this season, a calf injury in training sucking the life out of his bid for inclusion.
The fulcrum of their game plan, Devin Toner, has given way to an ankle injury in a rare missed match.
Worse again, today's opponents Toulouse have serious reinforcements from their 28-27 win in Stade Ernest Wallon.
The formidable shape of World Cup winner Jerome Kaino will be backed up by lock Richie Arnold - he is the equally large twin brother to Rory - French internationals Antoine Dupont and Yoann Huget as well as up and coming flanker Francois Cros.
It is just a simple fact that Toulouse have grown stronger, while Leinster have had their options shrunk by the misfortune of injury.
The loss of Toner will increase the responsibility on the shoulders of either Scott Fardy or James Ryan to take on the mantle of the lineout caller.
The set-piece is the bedrock of Leinster's strategy, especially in terms of winning the ball and treating it like a precious gem.
The scrum has to be stable, even gaining forward momentum, under the leadership of Tadhg Furlong.
There is also the notable inclusion of Ed Byrne on the bench ahead of Jack McGrath in a decision that raised the greyest eyebrows.
It is the first significant step in Byrne challenging the Cian Healy-McGrath one-two punch that has sustained Leinster and Ireland.
As Stuart Lancaster revealed earlier in the week, Toulouse have scored over 50pc of their tries from turnover ball.
This places a priority on Leinster not being loose with the ball when they have it.
The best way to do this is to take a low-risk route to victory, using tempo to dictate a multi-phase attack.
Coach Leo Cullen can still call on a pack of forwards with the steel spine of Healy, Furlong, Fardy, Ryan, Rhys Ruddock, Josh van der Flier and Jack Conan.
It is up front where Toulouse must be taken to task and kept to it.
"Learning from the experience of playing them over there, they really got a handle of us physically," said captain Ruddock.
"From the first minute, they were looking to smother us and looking to impose themselves on us.
"So, just to learn from that and make sure that we're the ones who are winning those collisions and putting the rest of the team on the front foot."
As long as Leinster can starve the French side of possession, they will grow hungry, desperate even, to show what they can do.
It is then the spectre of indiscipline could well become a factor.
This is where Ross Byrne can come into his own.
For, the best single aspect of his game is his line-kicking, closely followed by cross-field balls for Adam Byrne or Dave Kearney - as well as his goal-kicking.
It is not in Leinster's DNA to build a lead in threes when tries are their preferred way to apply what they call 'scoreboard pressure'.
The secret to success can be traced to the kick-off when the home side has to establish dominance, suffocate Toulouse from the get-go and squeeze the life out of them.
Forget about Leinster being the hunted, now that they are champions.
They have to show Toulouse why they were able to bridge the six-year gap from 2012 to 2018.
This is the moment when all those chances offered up by Cullen will have to be delivered on in a big game, not in PRO14 routs of Ospreys, Dragons and Ulster.
This is the time for Rory O'Loughlin, playing out of position, the rejuvenated Adam Byrne and the returning Dave Kearney to show they are as good as they have shown in patches this season.
It will be far from easy.
Leinster: J Larmour; A Byrne, G Ringrose, R O'Loughlin, D Kearney; R Byrne, L McGrath; C Healy, S Cronin, T Furlong, S Fardy, J Ryan, R Ruddock (capt), J van der Flier, J Conan.
Replacements: J Tracy, E Byrne, A Porter, R Molony, M Deegan; J Gibson-Park, N Reid, C O'Brien.
Toulouse: M Medard; C Kolbe, S Guitoune, R N'Tamack, Y Huget; T Ramos, A Dupont; C Castets, J Marchand, C Faumuina, R Arnold, J Tekori, F Cros, R Elstadt, J Kaino.
Replacements: P Mauvaka, C Baille, D Aldegheri, P Faasalele, L Madaule; A Placines, S Bezy, Z Holmes.