Boss Chris Wilder admitted a ‘rubbish start’ cost his Cobblers side dear as Cambridge United claimed three points at sun-drenched Sixfields.
A first-minute Harrison Dunk effort secured a 1-0 victory for the U’s, who had not won any of their previous seven Sky Bet League Two games.
Richard Money’s men shut up shop and starved the Cobblers of meaningful opportunities as Wilder’s men pushed for a breakthrough.
It means Cobblers are now five points adrift of the play-off places with just five games remaining.
And Wilder was left ruing a sluggish start as his men missed a chance to move closer to the top seven.
“It was a rubbish start and they were better than us, which gave them a massive lift,” said the Town manager.
“You talk about teams being on a bad run and we stressed over the weekend that we couldn’t afford to give them an opportunity to go ahead in the game and we have done.
“We committed too many people forward in the first minute, the goalkeeper should do better and it’s given them a massive boost.
“It gave them a lift, it deflated us.”
Wilder made a change after just 30 minutes as he brought on Ivan Toney for winger Chris Hackett in a bid to kick-start a Cobblers charge.
But despite huffing and puffing, they couldn’t blow the Cambridge door down.
“We decided to make the change because they were sat that deep and there was no room in behind,” said Wilder.
“We had to move the ball in front of them and we weren’t really doing it that well.
“We were always going to get caught on the counter-attack with the amount of people we were chucking forward and there were a couple of opportunities for them in the second half.
“But I wasn’t disappointed with the players’ commitment, character or attitude, I was just disappointed that when we got into the final third, we never produced anything of any quality.”