Chris Wilder admitted the Cobblers’ form is ‘not good enough’ at the moment and refused to cite the club’s long injury list as a factor.
Town suffered a fourth straight defeat when Luke Guttridge’s 90th-minute goal put the seal on a 1-0 win for Luton at a sold-out Kenilworth Road.
It is a result which puts the Hatters top of Sky Bet League Two, while Northampton slip to 18th in the table, with their manager Wilder furious once again.
“I’m disappointed for the fantastic support we took to the game and people will talk about them leaving it late to score,” he said.
“But we haven’t got anything from the football match and it isn’t good enough, regardless of what else we’ve got going on with people missing.
“In the big moments of the game we weren’t good enough - if we were better we’d have won but we weren’t and they were in their big moment.
“It was a fantastic finish by (Luke) Guttridge and he’s decided the match. We need to take our opportunities in games to avoid putting ourselves under pressure.”
Luton were not at their best in a game of few chances in which Alex Nicholls came closest to scoring for the Cobblers in the second half.
But the Hatters’ ability to take control in the ‘big moments’ was the reason behind their victory, according to Wilder.
“I didn’t think they caused us too many problems,” he said. “We needed to stay calm and composed when the bullets are flying around and they were when we weren’t.
“When we broke the play up we gave them opportunities to put it back on us because we didn’t do enough with the ball.
“Our goalkeeper didn’t have many saves to make but then he had one to make and the ball has ended up in the back of our net.”