In boxing parlance, the champions of Europe lost in a non-title bout on Saturday. However, the manner rather than the scale of the loss will hurt the Leinster players and management more, because they played without wit or vision against what even now is an inferior force.
Joe Schmidt, who has had a honeymoon of soft-focus interviews from "fans with typewriters", should face some hard questions after this performance. He is not the first coach to underestimate Munster in their own backyard, but he does have to explain why his team opened in such a tame and error-strewn fashion.
Why also did they show such little respect for their opponents, in attempting to play fast and loose with the elements behind them?
On one occasion they put half a dozen passes across the backline, 10 metres from their own line before Brian O'Driscoll, as he did often thereafter, hoofed the ball aimlessly upfield.
Then, crucially, with the result in the balance, Schmidt took off Richardt Strauss, Mike Ross and Sean O'Brien, the architects of his team's success all season. At a stroke, he handed the initiative to Munster. Being humiliated at the scrum by Northampton is one thing; suffering the indignity of conceding a penalty try to one of the least offensive set-pieces in Europe is something else entirely.
"Fatigue was the issue," explained the coach. Yet anybody that suggested the same for Northampton last week was deemed to be ungenerous to the grandeur of the Leinster comeback.
Strategy rather than tiredness was at the root of the failure. Jonny Sexton rarely kicked for position, preferring to slavishly feed his outside backs, who wore themselves out fruitlessly charging against an impregnable Red defence.
Not for the first time, Ronan O'Gara put a young pretender in his place. The veteran No 10 was a heroic defender, controlled the game with pass and kick, and delivered the highlight of the game with an inch-perfect delivery to Keith Earls.
The battle for the Ireland fly-half shirt is far from over, and with Italy likely to be the defining fixture of the World Cup, Declan Kidney may well decide to start with a man who can give control under intense pressure.
Half-backs and back-rows decide matches. O'Brien, as with last week, proved he can only operate off go-forward ball and again he was denied that advantage. Jamie Heaslip, as he has been too often this season, was a peripheral figure and never led from the front. Behind them, Eoin Reddan was slow in delivery and uncertain in decision.
In contrast, David Wallace was a giant and James Coughlan displayed hitherto unseen talents backed up by an abrasive Donnacha Ryan. However, Conor Murray was the success of the evening, moving his substantial frame into contention for the trip to New Zealand. He passed fast and accurately, forsook the now obligatory four steps and was a constant threat on the break.
Luke Fitzgerald is now being selected on reputation and potential rather than form and he had another bad day. He was left hopelessly in no man's land for Doug Howlett's try and still does not appear to have grasped the fundamental lesson that leaving the wing means that man and ball must be taken inside. It was no coincidence that Munster's primary gains were made down his wing, as time and again he stood off his opposite number.
One thunderous tackle failed to disguise that he is not currently good enough for Leinster, let alone Ireland. He was overshadowed by Earls, and Felix Jones gave him a lesson in how a full-back should defend. The youngster looked the best Irish No 15 since Hugo MacNeill.
Still, worries remain that this team can be a force in Europe. On Saturday they faced a team with a poor game plan, below par in all the important areas and possibly tired. The Heineken Cup draw will give Munster a difficult group and the prospect of facing teams with sharper minds and attitudes. As this year proved, games in the Magners League can be won without the cutting edge required to beat the best that England and France have to offer.
However, let us rejoice that the magnificent spirit and pride that for over a decade carried the lone flag for Ireland in Europe is alive and well. It was epitomised by the extraordinary sight of John Hayes going the full 80 minutes for his team. His performance overshadowed the cheap antics of his front-row colleague Marcus Horan.
Thomond Park, unlike the Millennium Stadium, was the site for a true contest, which was engrossing to the very end in the best traditions of the fixture between these teams.