Manager Rob Page blamed defensive lapses and poor decision making for the Cobblers' 3-1 defeat at Chesterfield on Saturday.
Northampton suffered their first Sky Bet League defeat since December last year, and Page felt his team lost because they simply weren't as strong defensively as they have been to date this season.
Chesterfield opened the scoring on eight minutes through Conor Wilkinson, who took advantage of a slight hesitation from Zander Diamond expecting an offside flag, and then doubled their lead four minutes into the second half when a Wilkinson shot took a huge deflection to wrong-foot goalkeeper Adam Smith.
Paul Anderson's first goal for the Cobblers on 63 minutes brought the visitors back into the match, but more sloppy play and defending just seven minutes later allowed Dion Donohue to make it 3-1 and seal the points.
"You can look at all three goals, and we have had a couple of deflections, and it was disappointing from that point of view," said Page..
"Defensively all season we have looked outstanding and every single man has put a shift in, but at this level if one or two just switch off then you get punished, and that's what happened.
"Chesterfield didn't have to work too hard for their goals, and we gifted them to them a little bit, which is something we can correct. If we had been torn apart today then I would be worried, but we haven't been.
"We gave the ball away too cheaply at times, defensively we were far too stretched, and maybe that is because we were on this run.
"We were full of confidence coming into the game, and perhaps we should have been a little bit more disciplined in our defending, as we have been irrespective of playing home or away.
"We have built that foundation to go on, because we will always score goals due to the quality we have in the team. But without that defensive organisation and hard work, at this level you run the risk of conceding goals."
The Cobblers never really got into top gear at the Proact Stadium, but Page felt his side should have been handed an early opportunity to score before Wilkinson's opener, with Alex Revell looking like he was pushed in the back by Spireites defender Tom Anderson.
"We should have had a penalty after four minutes," said the Town boss. "Everybody in the stadium could see, the fourth official tells me it's a penalty, he sees what I see, and it is a two-handed push in the back of Revs.
"The referee doesn't give it, and I think if the defender does that in the 20th minute then it's a penalty. It was a big decision, and he didn't give it, and then we concede the goal in the manner we did."
The Town boss wasn't too disheartened by the loss at Chesterfield in the greater scheme of things, and believes his squad will quickly bounce back - starting with Wednesday night's big EFL Cup clash with Premier League giants Manchester United at a sold-out Sixfields.
"I have said it to the boys, the test now is how we react to this," said Page.
"We were always going to get that defeat sooner or later, it's how we react now and I know the characters we have in that dressing room.
"They are hurting at the minute as nobody likes losing a game of football, and we have lost today, but I know there will be a positive reaction, and there is no better game than Wednesday night for that to happen in."