Hands up those who saw this one coming -- but count me out. Back in October, an astonishing 30 points separated the teams at the death; last Friday, the difference was just a single point.
But, trust me, for Munster this latest defeat -- the third on the bounce to their great rivals -- was even more crushing than that suffered at the RDS. And, for Leinster to win at Thomond Park in such a manner would have been even more satisfying than that Dublin 4 romp.
For Michael Cheika and Leinster, this was a massive achievement. The challenge now, and it is significant, is to bring everyone involved back to reality and focus on what lies ahead at the RDS on Friday.
In contrast to Leinster, Clermont Auvergne were poor in defeat to Stade Francais in Paris last Saturday. Collective confidence added to home comfort ought to put the reigning Heineken Cup champions clearly in pole position, but rugby doesn't work like that.
Psychology -- individual and collective -- has such a vital part to play. It is why I thought Munster would win this Good Friday showdown. But, as illustrated again by Cheika in his post-match comments, it is why he and his team have become such a formidable and consistent competitive force when the chips are down and that really big performance is demanded.
"We're trying to get the team peaked at the right time as there are a few different cycles going on. Against Clermont there will be a bit of fresh energy to bring back to the team so it's about understanding what happened here (in Limerick) and the core elements that brought it about."
The different cycles to which he relates are Six Nations, Magners League and Heineken Cup. It is a difficult balancing act, hence the need for clearly defined peaks and semi troughs but all underpinned by core physicality in defensive alignment and competitiveness at the breakdown. Other elements can lend to that 'switch on/switch off' mentality but the 'core' to which Cheika so rightly refers to is not negotiable.
The day of ladyboy rugby is long a thing of the past. Leinster will lose to Munster again sometime in the future -- of that I have no doubt -- but any time they do, it will be hard earned.
The 'soft centre' jibe no longer applies. Irrespective of what happens in terms of silverware in the coming months, Cheika's input to Leinster rugby has been immense. He, Jono Gibbes and Kurt McQuilkin have instilled not just a winning mentality but a tough, physical forward-oriented psyche too.
Everything was set up for a Munster win, even without Paul O'Connell. Just how badly he was missed as a leader reflects poorly on the southern province at this point in time.
You can't tell me that the loss of Brian O'Driscoll was any less damaging in terms of morale to Leinster than O'Connell's absence was to Munster. Equally so Shane Horgan (another massive presence within this Leinster squad) against the attacking spark that is Keith Earls. In effect, these omissions cancelled each other out. But with Leinster you would hardly have known.
Were a combined team picked in the immediate aftermath, what Munster players would have made it? Jerry Flannery, Mick O'Driscoll, Alan Quinlan and Ronan O'Gara perhaps. Jean de Villiers possibly but, beyond that, it was Leinster taking all the individual scraps of consequence. They controlled the second half and nobody could deny Leinster their hard-fought win.
Leinster had big performers in every line with Stan Wright, Jamie Heaslip, Eoin Reddan, Isa Nacewa and Rob Kearney running hot.
For me, Heaslip continues to be an Irish skipper-in-waiting. Whether on front foot or back, there is an inherent honesty to his game you simply cannot buy. He is an integral factor in the shift of Leinster mindset. He is a cross between Anthony Foley and Victor Costello and already up there alongside Willie Duggan as the best-ever No 8 Ireland has ever seen.
In the much-hyped out-half battle, we learned little we didn't already know. Declan Kidney does have a problem because, were a team being picked right now, I suspect he would struggle to give a definitive nod either way with any degree of confidence.
Jonathan Sexton is mixing with demons. O'Gara was the more composed playmaker (and goalkicker) on Friday, yet must accept full culpability for effectively giving the game away. His rash penalty concession was mindless in the extreme. He knows that better than anyone else. Composed leadership it most certainly was not.
All told it adds an extra dimension to the end-of-season tour. With hand on heart I don't know which one is in front but, I suspect on overall form of late, that it is the Munster man marginally ahead.
That of course is of little solace to Tony McGahan or Munster. Friday's defeat leaves the reigning champions in a dogfight with Edinburgh, Glasgow and the Ospreys for the three remaining play-off places. Of more immediate concern is the Heineken Cup visit of Northampton in four days time.
Falling to Leinster at Fortress Thomond is the last thing needed ahead of Saturday's must-win game. The general consensus seems to be that the seeds to becoming only the second team (after Leicester) to win in Limerick in the Heineken Cup were sown by Northampton at the same venue in January.
Under Jim Mallinder, the Saints are becoming a significant Premiership force but, would I bet against another circling of the wagons and a Munster march to the semi-final stage? No, nay never.
Call it reverse psychology, but last weekend's defeat might be just the incentive needed to kick on from here. For Northampton, unlike in January, the heat is on with expectations high. Heineken Cup evenings like this are made for -- and made in -- Munster.
Leinster, by contrast, need to be wary. They are up against arguably the most dangerous -- and certainly the most physical -- of the eight remaining but, like Munster, they can build on last Friday's intensity.
And isn't it nice for a change to see so much Irish attention focus on Connacht as the western province's two-pronged attack on that Heineken Cup breakthrough takes shape. Last weekend's superb win over Magners League-chasing Edinburgh sets up a genuine scrap with disappointing Ulster for the third guaranteed Irish Heineken Cup slot. It could yet come down to that final game of the campaign at Ravenhill in May.
But, first thing's first, and the visit of Bourgoin to Galway for the Amlin Challenge Cup quarter-final when -- for once -- the Sportsground will brim with bodies and atmosphere.
Whether it be through the Challenge Cup or the Magners League, could there be a more appropriate way for Michael Bradley to sign off his time with Connacht rugby than by delivering in Europe?