Jim Mallinder thanked the Saints supporters for providing the inspiration his side needed to earn a dramatic victory against Stade Français on Friday night.
The atmosphere at Franklin's Gardens was electric as the home fans roared their team to a 23-22 victory in the Champions Cup play-off final.
It came despite Saints being down to 13 men at one point, with Rory Hutchinson in the sin bin and Tom Wood sent off for making contact with the face of Djibril Camara with his boot.
Ahsee Tuala kept his composure to bag a crucial try six minutes from time and Harry Mallinder's nerveless conversion won the game for Saints.
It means Jim Mallinder's men, who were 22-9 down at half-time, will be playing in the Champions Cup next season.
And the Saints boss said: "The crowd were absolutely magnificent.
"I've not heard them as noisy as that over the last few years and a lot of credit to the fans for getting behind the team and supporting us because it has been a long season.
"It's three weeks since we beat Harlequins (on the final day of the Aviva Premiership regular season) here and it's been a long three weeks, but it is nice to get the win."
Tuala's try, which added to an earlier effort from Ben Foden, brought back memories of the stunning scenes of May, 2014, when Wood scored a try that helped 14-man Saints see off Leicester Tigers in the Premiership semi-final.
And when asked if Tuala's effort reminded him of that moment, Mallinder said: "It was similar in terms of the crowd and the reaction after we lost two men.
"The fans were absolutely fantastic and it inspired the players to be honest.
"Those lads who came on did a remarkable job."
Saints would have dropped into the Challenge Cup if they had lost to Stade.
But they can now look forward to the Champions Cup draw on June 8.
"What we look for in terms of the squad of players is to compete at the highest level," Mallinder said.
"That's what we want and that's what the fans want. They want top class rugby here and that's the competition we want to play in."