Regrets, Saints would have had a few when they landed back at Luton airport on Sunday afternoon.
Because while one losing bonus point was safely tucked away in the suitcase, three more remained on the Stade Pierre-Antoine pitch.
Saints went to Castres and stood up to the challenge presented by the French champions.
In fact, they did more than stand up. They stood up and shouted at the top of their voice, but yet they weren’t heard when it mattered.
Chances came and went, while Castres were more clinical as they took every opportunity presented to them.
Romain Martial’s try, handed to him on a plate by Luther Burrell’s pass, and 14 points from the metronome that is Rory Kockott was the sum total of their forays into Saints territory.
The game was largely played in the French team’s half, but, to their credit, they stuck manfully to their task, defending as Saints endeavoured to knock the door down.
Whether Castres will hold out with such mite in the later rounds of the competition should they start to struggle remains to be seen.
But they certainly irked a Northampton team, who, aside from skipper Dylan Hartley’s opportunistic try, lacked any real ruthlessness in enemy territory.
It was a similar story to the one at Leicester a week earlier as they had the possession to comfortably win the game. But when it mattered, they were unable to make it pay.
Supporters summed it up after the game, with social networking sites saturated with one word: Frustration.
“Why do I support the most frustrating rugby team on the whole planet,” tweeted one supporter.
“Saints are talented, powerful, dominant, experienced... & the most frustrating team around!” added another.
And Jim Mallinder and Hartley didn’t waste any time in making similar statements during their post-match interviews.
Neither man was too downbeat, though. They know there is a long way to go in this competition. Five more games that will decide their European fate.
But a big dollop of pressure has been placed on Sunday’s showdown with Ospreys at Franklin’s Gardens.
The Welsh side were opening-day casualties, too, being hurt at home by Leinster, who claimed a 19-9 win at the Liberty Stadium.
It’s first blood to the Irish and French, while Saints were left to wonder what might have been on their return to English soil.
How they rated...
Stuggled to get into the game and saw yellow before half-time, which clearly didn’t help Saints’ cause... 5
Didn’t have much impact in attack and coughed up the ball on one or two occasions with Saints on the front foot... 5
Like his fellow Saints backs, struggled to break down a stubborn Castres rearguard and had less joy than at Leicester a week earlier... 6
Was involved in the key moment of the game as his pass went into the hands of Romain Martial, who raced home to score... 5
Tried his best to get into the game, continually looking for the ball, but struggled to make much ground as Castres pressed well... 6
Only one missed kick from the fly-half, who continued his good season with the boot, but was unable to pull the strings as he had at Tigers... 6
Fizzed the ball around well, especially during the first half, but is clearly still getting to know his team-mates after rotating with Lee Dickson... 6
Helped Saints hold up well against a big Castres pack and is growing into his new club’s shirt week by week... 7
Made the most of his one try-scoring opportunity, capitalising on a Castres mistake to stretch over the line and, generally, had a good game... 7
Did exactly what it said on the tin, as he helped Saints compete at the scrum and ensured they were better in that area than at Leicester. A good first start... 7
COURTNEY LAWES - CHRON STAR MAN
Again the pick of the Saints bunch as he excelled in open play and in the lineout. England take note... 7
The experienced second row was back in the side after a week off with injury and he was a welcome addition... 7
Foraged well and showed some real determination to try to get Saints over the gain line. Leads by example... 7
Was on the wrong end of a couple of penalty decisions but didn’t have too bad an afternoon overall... 6
Was unable to make the massive impact he has done regularly early in the season and was eventually replaced by Samu Manoa... 6
Replacements (who played more than 20 minutes)
TOM MERCEY (for Ma’afu 59)
Came on to add a freshness to the scrum and kept Saints going forward as they searched for at least a point... 6
SAMU MANOA (for Dickinson 59)
A great man to bring off the bench, adding power to the side, but even he couldn’t make Castres crack... 6
LEE DICKSON (for Fotuali’i 59)
Always increases the tempo and continued his fine season with another sparky display... 7