Comment: With Johnny Sexton given the evening off, battle of the back fives will determine the outcome of a demolition derby
Ten men hold the key to the bragging rights on offer in Ballsbridge this evening.
Much of the focus this week has centred on the No 10s who might and might not play, but the playmakers need the ball to perform and the contest for that ball will be ferocious.
It is feasible that all of the second-rows and back-rows on display could be on the plane to Japan in less than a year's time. Some have more to do than others, but they are all international calibre.
More than any other, the tackle area determines the outcome of these big games and the tone for these interprovincial derbies is set at the ruck.
Rarely does one team get the full squeeze on at the set-piece, there are game-breakers in both backlines and with Johnny Sexton up in the stands there is little difference at half-back.
No, this one is about the big boys in the trenches who will be tasked with winning enough go-forward possession for their team to secure the spoils.
On the blue side of the equation, there is the tantalising double-whammy of Dan Leavy and Seán O'Brien working in tandem with Rhys Ruddock carrying the slack.
O'Brien sat out yesterday's final training session at the Aviva Stadium, but Leinster are confident he'll start.
In front of them, the pairing of Devin Toner and James Ryan is international class and capable of doing real damage.
Up against those two is the newer combination of Jean Kleyn and Tadhg Beirne who look well matched, while the trio of Peter O'Mahony, Tommy O'Donnell and CJ Stander is more than capable of a big performance.
The presence of Josh van der Flier and Chris Cloete on the bench adds to the back-row intrigue, both men will bring a different sort of relentless energy when introduced.
Blitzed Munster have gone away from home twice this season and been blitzed at the breakdown. The Red Army will see their ruck performance as a red-line issue.
In Glasgow and Cardiff, they struggled to lay a glove on the opposition ball which, in turn, put their defence under pressure. At home they've had far more joy in slowing the ball down, but their opposition has been poor.
Tonight, they'll have a truer barometer of where they stand ahead of their daunting trip to Exeter next weekend.
The breakdown, of course, is the responsibility of all 30 players, but it is the back-rows and second-rows who will spend most of their time in the heat of the battle.
For Leinster, it sets the tone in every game. They have developed a capacity to beat teams at their own game, relentlessly driving the ball in tight or bringing their talented backline into the equation. They are shy some big names, with Sexton joined in the stands by Garry Ringrose, Jordan Larmour, Joe Tomane, Tadhg Furlong, Scott Fardy and Jack Conan.
It is a testament to their squad that they can name a team with 12 Ireland internationals, with two uncapped players with real ambitions of making the World Cup squad at half-back in not-yet-qualified Jamison Gibson-Park and Ross Byrne as well as the supremely talented James Lowe making up the numbers.
Byrne's clash with Joey Carbery is a fascinating sub-plot.
Carbery has the caps and attracts the headlines, but it is Byrne who was backed by Leinster when they needed a back-up No 10 to Sexton.
He lacks the game-breaking pace of his old rival, but he fits snugly into the Blues' game-plan and has a good habit of making good decisions.
It helps that he is generally playing behind a dominant pack, but his kicking-game is strong while he is composed when orchestrating those around him.
Carbery plays with the handbrake off and is capable of breathtaking moments, but his lack of time in the jersey means he is still prone to the odd rash decision.
Leinster will have taken plenty from Cardiff's capacity to get pressure on the 22-year-old and they'll know his tells more than anyone else.
Having opted to head down to Munster in search of game-time, he can expect plenty of big Leinster ball-carriers like Robbie Henshaw heading down his channel.
Alby Mathewson is an interesting addition to the equation, bringing huge experience to the party and bridging the gap in quality as Conor Murray continues his mystery absence.
The Kiwi was hugely impressive against a pitiful Ulster effort and can expect messier ball today, but it's nothing he hasn't seen before.
As a quirk of the conference system, this game no longer pits two direct rivals against each other and Cullen conceded that played a part in his decision not to select a full-strength team.
Yet it doesn't lack for bite, according to Leinster captain Ruddock.
"It is just that intensity, that physicality," he said of the game.
"It can start out as a bit of an arm-wrestle but then the game gets played at a high intensity and a fast pace which is, as I said, an equivalent of European games.
"It is hugely physical and that stands to us. As well, there is the emotion that the players carry into the game, if you ask any players which game they look forward too I'm sure they will tell you this one.
"Last week (against Connacht) certainly felt like another step up in terms of physicality and intensity it was played at and then every Munster game I've played in it has been right up there with Europe in that sense.
"The commitment, the physicality of the players, and we're expecting this weekend to be all those in terms of being up there with Europe. It is a good lead-in but it takes its toll, and are physical encounters all the same."
Ostensibly, that's what this fixture has long been about: getting the teams ready for the step up to come.
With four wins from five and a short turnaround to Wasps' visit to the RDS next Friday, Leinster could be forgiven for taking their eyes off the ball.
Munster's need is probably greater, particularly as they lurch from comfortable home win to disappointing away performance.
As they make the trip, their fans will be acutely aware that Leinster's rotated team beat their full XV twice last season.
Their record in this stadium is poor and Johann van Graan is fully aware of the challenge.
"There is no place to hide," he said. "You have to go out there and be at your best, both mentally and physically, to beat them."
If they are to get the better of their old foes from the east, it will start and end in the tight. Getting the better of this Leinster pack will set them fair against all-comers from Europe, but another defeat on the road leaves them with huge questions ahead of Sandy Park.
So, the pressure looks to be on the visiting side's shoulders which will suit Leinster down to the ground.
Even without their leading man, they'll be confident of keeping the show on the road.