Cobblers boss Jimmy Floyd Hasselbaink admitted he was left worried by the manner of his side's 'flat' performance after they were 'played off the park' by Rochdale in Saturday's 1-0 defeat at Sixfields.
The two relegation battlers looked worlds apart as Rochdale dominated most of the game to deservedly leave Sixfields with their first away league win of the season and their first league win of any kind since November.
Calvin Andrew scored the only goal, converting Matt Done's left-wing cross eight minutes into the second-half, to end Town's four-game unbeaten run and keep them just one point above the drop zone in Sky Bet League One.
Hasselbaink had made changes to the team which drew at Blackburn Rovers in their previous game, bringing in Sam Foley and Hildeberto Pereira, but they did not have the desired impact as Town turned in one of their most disappointing displays of the season.
He afterwards: "Hindsight if a beautiful thing but I felt that, playing at home, we wanted to be more attack-minded and I must say that Rochdale were better today, much better and they deserved the three points.
"They played us off the park and that is worrying for me because we didn't deserve anything from the game and I don't think that was down to the changes I made.
"If you look against Blackburn, I made changes for that game as well. I thought we were flat, really flat, and we were poor with and without the ball.
"We were all off it. The performance was a total contrast to the past four games so we have to make sure it's just a one off and put it right next time.
"It's a step back for us but now we need to react for the next match and make sure that we are right for it and have a response and move forward."
The Cobblers were not helped by an injury suffered by right-back Shay Facey in the first-half. With no Brendan Moloney on the bench, Hasselbaink was forced to bring on centre-back Regan Poole and switch to 3-5-2 with Foley and Joe Bunney playing as wing-backs.
That only made things worse, however, and allowed Rochdale to assert their superiority even more, with Andrew's second-half winner the least they deserved from the game.
"Normally I would have had Brendan on the bench but he had a problem with his knee on Friday and he wasn't sure if he could make it if something happened to the full-back in the first 10 minutes," added the Town boss.
"We didn't take the chance to put him on the bench and that was a problem. If he's on the bench, you go like for like and the formation stays the same and you work from there, but it wasn't to be."
On Facey's injury, Hasselbaink continued: "It's a hamstring problem and I don't think it's good news. He's not the kind of boy who would just come off the pitch so it's a hamstring and we'll see."