December in the Heineken Cup offers fixtures that are mirror images of each other. What happens in those fixtures is rarely replicated, however.
The English side will never again this season turn over 27 possessions; it is highly unlikely that Leinster will face top-class opposition who will so blithely cough up ball.
Northampton will improve -- they must. History has demonstrated that they can, whether at Ravenhill last season or, domestically, when emerging from the fog of home trimmings by Leicester or Gloucester.
Anyone who misinterprets the evidence of last Saturday's self-confessed non-showing only has to review the evidence of their filleting of Saracens in the Premiership semi-final.
Leinster do not need to be alerted to much of this. Their focus has been internal; their set-piece may have cost them dearly against better competitors and they were often shoddy with the ball themselves. Not when it mattered, however. The early blitz set the tone. Northampton, for some bizarre reason, weren't prepared for the raucous intensity served up by Leinster.
Seven days later, the English side will seek atonement -- the Saints may become temporary sinners to prove a point.
But, just as Jamie Heaslip dismissed the pointed attempts of Dylan Hartley to rile him in Franklin's Gardens, Leinster must ignore any attempts by the English side to get them to submit to their level.
In many respects, given the level of anticipation surrounding this Leinster side following last week's result, this could be a fixture full of peril were they unprepared mentally.
"These are the weeks that really test you and it's what all the best teams can do -- back up a good performance," admits Luke Fitzgerald. "This is definitely the most dangerous match we will play this year if we don't match last week's levels."
His coach renews this appeal to his side's sense of professional duty.
"We didn't really exert enough pressure on them at set-pieces," says Matt O'Connor, when pressed to sift through the extraordinary result for pockets of regret. "There were bits in our defence that weren't good enough. I thought our attitude was good, but we are going to have to make sure that all the little things that make the big moments are spot on this week.
"They are coming, in many respects, in a more dangerous frame of mind because they have nothing to lose, so we have to be sure that we are that little bit more accurate across the board."
Aside from the key return of scrum-half Kahn Fotuali'i to the bench, Northampton's three changes in the pack will ensure Leinster won't contemplate taking a backward step.
With Salesi Ma'afu, Christian Day and Calum Clark all returning to the starting 15, the opening few minutes of this one may not be for the faint of heart. Surprisingly, Ken Pisi is named at full-back; whether he reprises his hapless turn there when the game kicks off is another matter.
Ma'afu has recovered from the foot injury which kept him out of last weekend's game, while Day and Clark come in for Sam Dickinson and Phil Dowson, who drop to the bench, shifting Tom Wood to the open-side. Numbers on the jersey are irrelevant; the question is whether their pride can fill them.
"I doubt that will be an issue," O'Connor observes when asked to assess the Northampton mindset this week.
"They're a really proud club and they've a long tradition at being very good. Irrespective of the result, they'll come with a very steely mentality to try to get something out of it, if nothing more than a lot better team performance.
"They spoke themselves about being embarrassed. And they're going to put everything into a really massive performance. The margins are pretty small. I mean, we were pretty good in the first 20 minutes last week.
"But you sit down and look at it and there are bits that can go either way. We're not silly, we know a bounce of a ball, a refereeing decision or inaccuracy from us can make it a different scoreline, a different result."
Predictably, Leinster's 23-man squad remains unchanged and O'Connor is hoping for a similar response from all -- particularly from Ian Madigan, who responded to the coach's faith in him last weekend.
"He was very good against Scarlets the previous week," asserts O'Connor. "He was very good in the Irish environment and he probably played more in that environment than most of us would have predicted.
"I said from day one that it was going to be a matter of time for Ian to get his head around what we were trying to do.
"I thought he was brilliant last week, the accuracy of his game, the way he managed us around the field was brilliant and if he continues to do that, he will play a hell of a lot of rugby for us."
Same again from Leinster, then. Same result expected too, from the expectant Lansdowne Road crowd that may hit the 50,000 mark (tickets are still on sale).
And, while it may not be achieved in precisely the same manner as last week's astonishing assault, the bottom line is all that matters for Leinster as they home in on a vital home quarter-final next April.
Leinster -- R Kearney; D Kearney, B O'Driscoll, G D'Arcy, L Fitzgerald; I Madigan, E Reddan; J McGrath, S Cronin, M Ross; D Toner, M McCarthy; R Ruddock, S O'Brien, J Heaslip (capt). Reps: A Dundon, M Bent, M Moore, L Cullen, S Jennings, J Cooney, J Gopperth, Z Kirchner.
Northampton -- K Pisi; J Elliott, D Waldouck, L Burrell, G North; S Myler, L Dickson; A Waller, D Hartley (capt), S Ma'afu, C Lawes, C Day, C Clark, T Wood, S Manoa. Reps: M Haywood, E Waller, T Mercey, S Dickinson, P Dowson, K Fotuali'i, L Dickson, T Collins.
REF -- J Garces (France)
LEINSTER V NORTHAMPTON,
LIVE, SKY SPORTS 2, 6.0