THEY knew they needed to turn back the clock and that's what they did – and how. Munster didn't become the worst team in the world in Glasgow, no more than they became the best team in Europe at the Stoop yesterday.
But what they did do was revert to type and produce the type of controlled knockout rugby from the heart that makes them the team that more than any other makes this great Heineken Cup competition tick.
And while this was another consummate team victory on the road against the odds, don't underplay the role played by Paul O'Connell. Superman is indeed looking for his O'Connell pyjamas once again.
Where this freeman of Limerick went, everyone followed. Some players are blessed with presence but only a select few back it up with performance almost every time.
I wouldn't be so bold as to suggest a Lions place is sealed on the back of one massive performance, but if the watching Warren Gatland can afford to travel minus this colossus, he must have some squad.
In the first half, Harlequins won the battle of the kickers but Munster dominated territory and, much more importantly, dictated the tempo. In the process, they created the type of game they craved. Here was Munster doing what Munster do best, squeezing and scrapping, with O'Connell at the heart.
And there were others too in an opening 40 dominated by Munster almost everywhere bar the scoreboard. But they had the English Premiership champions where they wanted them, in the type of arm wrestle in which Munster rugby will forever thrive.
Munster trailed 9-6 at the break, with Ronan O'Gara uncharacteristically missing two early penalties, but it didn't take a genius to work out what the second-half strategy would be.
You knew by the body language going in that the team in red would emerge and give it everything. The aristocratic Londoners were rattled.
And when Munster are in a massive 'must win' situation such as this, once they sense blood, they go for it. In that third quarter, they threw everything at Conor O'Shea's Quins.
Within six minutes, they were ahead as Peter O'Mahony, James Coughlan, Donnacha Ryan, Tommy O'Donnell, James Downey, Simon Zebo and Conor Murray grew in confidence and influence. Murray and O'Mahony are definitely now in the Lions frame.
One cannot but feel for Declan Kidney with all these guys returning.
That said, credit Rob Penney for having the good sense to put that much heralded expansive strategy on hold. Instead, what we got was down-to-earth cup-winning rugby the Munster way. When delivered on occasions such as this, there are few better sights on a sporting field anywhere.
If the head coach didn't fully appreciate the significance of tradition from afar, I suspect he is well acquainted and utterly convinced now. There will be room for development in time but, when armed with assets that put the fear of God in the opposition, it is pure madness not to use them.
As I understand it, last weekend's Glasgow drubbing provided a reality check just in time, culminating in a major reassessment in midweek.
Far from being boring, Munster squeezing the opposition has an appeal all of its own. I suspect I wasn't alone in feeling immense pride as brilliant Munster went from a first half of building belief to a second half driving that significant advantage home.
What we witnessed in Munster was a side given free rein to play the type of rugby with which they are most comfortable. That competitive edge was back and it held Quins in a vice-like grip. No matter how hard they tried, they just couldn't break loose.
What Saracens did to Ulster on Saturday, Munster repeated yesterday. And for Owen Farrell at Twickenham, read the equally nerveless O'Gara at the Stoop.
Older, wiser, slower perhaps but coolness personified in translating field position and penalties into points. If O'Connell was the instigator then, true to form, O'Gara was the assassin in chief.
No trophy was won, but a great provincial team restored both its pride and that centre-stage position they are so used to.
I doubt Vern Cotter and Clermont will be over enamoured by this outcome. Whatever else, Montpellier can prepare for the ultimate invasion.