In the build-up to last night's quarter-final at Clermont, it was widely acknowledged that it would take by far the best Saints showing of the season if a win was to be claimed.
But what they eventually served up at Stade Marcel Michelin was far from that.
Individual errors, the failure to execute some basics - especially in the lineout - and a struggle to cope with Clermont's immense physicality proved extremely costly.
Costly to the tune of eight tries conceded in fact.
Saints went toe to toe with the French giants early on, displaying the confidence that has been so evident under boss Chris Boyd this season.
But things unraveled extremely quickly as Clermont managed to sneak in down the left before Saints opened the door for them twice more before the break.
First, James Fish's pass went astray, allowing Damain Penaud to pick up and charge home.
Then, Taqele Naiyaravoro made a decision that was even harder to take as his no-arms tackle on Arthur Iturria not only earned him a yellow card but gave away a penalty try.
At 22-3 down, Saints would have found it easier to climb one of the mountains that overlooks Stade Marcel Michelin rather than the one they faced on the field.
But after Clermont continued to twist the knife, the Top 14 giants showed one of their very few weaknesses, losing concentration again during the second half.
Just as they had back in January, when Saints pushed them all the way in a 48-40 pool stage defeat, Clermont started to leave gaps.
And Saints exploited them.
At first, there was warm applause in the stands as the home fans afforded their opponents some sympathy.
But the appreciation soon started to turn to angst as Saints started to cut Clermont apart with the slick attacking game that has been on show so often during the current campaign.
At 37-31 down with 14 minutes to go, it was certainly game on.
But once again, Clermont awoke from their slumber, eventually pulling away again to claim the win.
That they couldn't really get the home side's nerves jangling will be a big regret for Saints.
They got to within touching distance and then totally lost their grip on the game again, allowing the hosts to get off the hook.
But credit has to go to Clermont.
They are a formidable side, saturated with power, pace and precision.
And when you've got players who are that big and that good, every team in Europe would struggle to live with them.
Saints won't play many better teams than this and at least their young players have seen how high the bar is set in Europe.
They could have expected a slightly easier ride in the Challenge Cup this season, but, in truth, they have been playing Champions Cup opposition in Clermont.
The Top 14 giants will be back in Europe's top tier competition next season - and they should be among the favourites to win it.
So losing three times to them in a season should bring no shame.
But it does inspire a few regrets for Saints, who will believe they are better than what they showed on Sunday evening.
And now they must prove that in some big Premiership matches in the weeks to come.
If they can do that and secure a top-six finish, games against sides as good as Clermont will be more frequent next season.
And Saints will hope that their Challenge Cup experiences of 2018/19 can stand them in good stead if that Champions Cup place does come to fruition.
How they rated...
Constantly tried to probe for openings and did not look overawed by the occasion, but Clermont were simply too strong and he missed a few tackles... 5
Did some good things in attack, but had a huge task on his hands in defence as he squared up to the sizeable Alivereti Raka, who gave him real trouble all night... 5
Not an easy night defensively, but was Saints' most creative player once again as he pulled the strings during the second period, setting up a couple of tries and scoring one... 7
Tried to give Saints some go-forward but Clermont shut the centre down well and he wasn't able to have an influence... 5
Did well to set up what was almost a try for Cobus Reinach but had a really difficult night defensively and his no-arms tackle on Arthur Iturria was extremely costly... 4
Was not delighted to be taken off as Saints sought to rest players for their next game, having fallen behind during the first half. Didn't do much wrong at all... 5
Will feel he should have scored in the first half and couldn't get the joy he has so often in Saints colours this season... 5
The captain tried to get his team going with a couple of carries but Saints kept hitting a brick wall during the first half... 5
Produced one sublime offload but that was as good as it got in a really tough 36 minutes for the hooker, whose stray pass led to a try and who struggled to hit his man in the lineout... 4
Saints didn't do too badly at scrum time and the prop didn't do too much wrong on a tricky night... 5
Kept going until the end, etching his name on the scoresheet two minutes from time as he refused to let fatigue get the better of him... 6
Was unable to take one of the kick-offs that immediately let to a Clermont try but he did put his body on the line again... 5
Clermont combated Saints' power well and the England lock was eventually forced off early in the second period... 5
Prides himself on his high-energy performances but Clermont were ready to meet fire with fire in the back row battle... 5
Scored a hat-trick at Stade Marcel Michelin in January but try as he might, he couldn't have the same telling influence on this occasion... 5
Replacements (who played more than 20 minutes)
REECE MARSHALL (for Fish 36)
Managed to steady the ship in the set piece slightly and certainly put himself about in a bid to help Saints turn things around... 5
JAMIE GIBSON (for Lawes 46)
Produced one superb offload on the right wing that led to a score and was an assured presence... 7
FRANCOIS VAN WYK (for Waller 50)
Didn't do much wrong after coming on, making his tackles and trying to put himself about... 5
BEN FRANKS (for Hill 50)
The final 30 minutes were dominated by the backs, meaning the forwards just chugged along, and this man did okay... 5
ALEX MITCHELL (for Reinach 50)
Made one superb tackle to stop man mountain Peceli Yato in his tracks and then managed to etch his name on the scoresheet in a sparky display... 7
HEINRICH BRUSSOW (for Ludlam 54)
Wasn't able to have too much of an impact as the game started to be taken over by backs play... 5
AHSEE TUALA (for Biggar 54)
Helped Saints to step up a gear in attack, scoring one try and setting up another, but did palm the ball into Clermont possession from a kick-off, which proved costly... 6
LUTHER BURRELL (for Francis 54)
Was unable to stop a slaloming Tim Nanai Williams when the Clermont full-back scored, but he wasn't the only one, and he added plenty in attack, scoring and assisting... 7