Nic Groom admits Saints feel like they've blown it.
But the scrum-half insists the players will be ready to take their chance if they get a second shot at Champions Cup qualification in the coming weeks.
Saints finished seventh in the Aviva Premiership and, as it stands, they will be playing Challenge Cup rugby next season.
But they could still make the Champions Cup if Gloucester lose to Stade Français in the Challenge Cup final in Edinburgh on Friday night.
If that happens, Jim Mallinder's men would face a play-off match against Connacht at Franklin's Gardens on the following weekend.
Win that, and they would need to win another match at the Gardens, against the winner of the game between Stade Français and Cardiff Blues, to book a place in the Champions Cup.
If that fails, Saints will be in the Challenge Cup.
And Groom, who helped his team beat sixth-placed Harlequins 22-20 on the final day of the Aviva Premiership regular season on Saturday, said: “It's quite a strange one.
“We feel like we've blown it. Regardless of the scoreboard, we knew we had a job to do and we didn't do that. So it's not really a victory for us.
“If you take the repercussions of that out of the way, a win against Harlequins, you would take that any day.
“But I think we're disappointed by only winning by two points. I think we were a lot better than them.
“We did things on the field that really put us in good positions to score points. It should never have been that close.
“I reckon if we were looking at the game normally we'd be stoked with the win but definitely not happy enough with our performance.
“Let's be honest, waiting isn’t ideal for us, but like I say - we want to be playing on the big stage next year.
“It's what this club stands for, it's what this club's about.
“So if we do get that lifeline there'll be a huge effort from everyone to make sure that we do play in top-flight Europe next year.”