Chris Boyd says Saints didn't make Clermont work hard enough for their win on Sunday evening.
The black, green and gold shipped eight tries as they fell to a 61-38 defeat in the European Challenge Cup quarter-final at Stade Marcel Michelin.
Saints did manage to score five tries of their own, bringing the score back to 37-31 with 14 minutes to go.
But again some poor defending and individual errors cost them as Clermont pulled away once more to secure their place in the semi-finals.
"It's a bit of deja vu really - 180 points over two games and we scored enough points to win a game," said Boyd, who had seen his side lose 48-40 at Clermont in the pool stages.
"But even with the amount of risk we're prepared to take you can't afford to be that inaccurate and you have to make them work much harder for their points.
"We had some big defensive lapses that came back to bite us.
"The killers are getting a kick-off, dropping the kick-off and the guy runs through about eight tackles to score under the posts.
"You sit and think 'they haven't had to work very hard for that'.
"We had some lapses in individual skill execution, whether that was because the players were under physical or mental fatigue will be interesting to find out when we have a chat about it.
"At the end of the day, some of our process and individual skill didn't stand up under scrutiny and that was disappointing."
When asked whether the occasion got to his young team, Boyd said: "I'd be surprised if that was the case.
"We didn't really have a lot to lose.
"They were firm favourites but we talked about needing to control the tempo of the game, control the hall and impose ourselves on them, which we were unable to do.
"They put us under pressure immediately.
"I'd back Cobus (Reinach) to score that try early doors 99 times out of 100 but he got flipped on his back.
"Those were the little moments we lost.
"Credit to our guys for coming back and making it a six-point ball game - at that point I thought maybe we could keep applying that pressure, but it wasn't to be."