Cobblers boss Jimmy Floyd Hasselbaink made no excuses for his side and admitted he may have got his team selection wrong after their 'flat' performance in Boxing Day's 3-0 defeat at Doncaster Rovers.
Any momentum that Northampton may have been building following Saturday's draw with high-flying Blackburn Rovers was brought to an abrupt halt by a dismal performance and deserved defeat at the Keepmoat Stadium.
Rovers skipper James Coppinger set Doncaster on their way when stabbing in from close-range on 33 minutes before Niall Mason's penalty, awarded for a foul on ex-Cobbler John Marquis, doubled the home side's lead just prior to half-time.
Town marginally improved in the early moments of the second-half but Andy Butler's header put the gloss on Doncaster's victory and they could well have won by more had it not been for Matt Ingram's goalkeeping allied to some wasteful finishing.
"I'm very disappointed, we were flat and they deserved to win," admitted a dispirited Hasselbaink afterwards. "In the last two matches we played really well and you want to keep that going and try to get a little bit of momentum.
"We had a good chance to score when it was 1-0 but then straightaway they go up the pitch and score a second goal and that summed us up today.
"It's a little bit frustrating because we're up and down. We want to sustain our form and at this moment I can't put my finger on why we were so flat today.
"The intensity was so high in the last two matches, we had played really well and all of that kind of stuff but today we didn't look how I see them and I know how they can play and how I want them to play."
Hasselbaink made four changes to the team which played so well in Saturday's draw against Blackburn Roves and also switched the system by playing 4-4-2, but he admitted afterwards that, in hindsight, those alterations may have been an error
He added: "We changed a few things and maybe I got the selection wrong for this match, it's a possibility, but there was no oomph and you need oomph and character, especially when you go away and when you're in the position we are.
"We tried to inject that into them at half-time and we started a bit better but you still need intensity and we didn't show enough of that."
On the spot-kick which led to Doncaster's second, when Matt Grimes was deemed to have tripped Marquis, Hasselbaink said: "I don't think it was a penalty, the boy knew what he was doing. He came across on purpose and trips himself and he made contact with Grimes."