Ivan Toney’s fifth goal of the season was not enough to prevent the Cobblers from losing a fifth away league game of the campaign.
Town went down 2-1 at Cambridge United with Adam Cunnington and Ryan Bird’s goals eclipsing the one scored by Toney.
It was a wide-open game in which both teams had several chances but the Us had the better ones and took them, whereas the Cobblers were often reliant on moments of magic from Kaid Mohamed.
Town made seven changes from the side which started at Leyton Orient in the Johnstone’s Paint Trophy in midweek, with both full-backs, both central midfielders and the entire forward line all altered.
They also reverted to a 4-4-2 system, opting to match up with Cambridge, who lined up in the same way.
One of the players restored to the line-up, Marc Richards, had a decent headed chance early in the game but steered it wide at the back post after initially leading the attack for the corner from which the chance came.
Mohamed punctured the home defence with a left-to-right run and played a one-two with Chris Hackett which ended with Mohamed having a shot blocked away for a corner, which came to nothing.
Jordan Archer had to be at his sharpest at the other end to keep out an Adam Cunnington header from a cross by former Town trainee Greg Taylor.
It would have been a poor goal to concede but the save was still an important one.
Lee Collins reacted quickly to clear from Kwesi Appiah before the on-loan Crystal Palace striker could have a second touch of the ball in the six-yard box.
Mohamed had a stinging right-footed shot blocked with both hands by Chris Dunn in the Cambridge goal and after the defence made a mess of the clearance, Mohamed again had another shooting opportunity, slicing wide with his left foot.
Ryan Donaldson picked out Robbie Simpson with a perfectly-weighted pass behind the Cobblers defence but Archer was quickly off his line to block at the midfielder’s feet and Simpson struck shot a yard wide after advancing through the centre.
Cambridge probably didn’t want half-time to arrive when it did, such was the quality of their play, and five minutes after the restart they fell behind.
Toney appeared to be fouled on the run at the edge of the box but referee Trevor Kettle played advantage and the ball was worked to Hackett, who teased in a cross for Toney to head past Dunn.
The lead, though, lasted just two minutes, with Cunnington steering in a header at a corner to give the Us an immediate response.
It gave them some momentum in the game and provided Tom Champion with the confidence to strike a free-kick at goal from an unlikely angle, Archer saving well to his right.
Toney steered a header narrowly wide from 12 yards from a Stewart Murdoch cross deep on the right wing and Gregor Robertson drew an excellent save from Dunn with a sizzling volley.
Minutes later, Cambridge took the lead when Appiah burst in behind the defence and although Ryan Cresswell made an initial tackle on the striker, he was still able to pick out Bird who, though off balance, steered a shot into the bottom corner.
Northampton finished the game with Cresswell playing as an emergency centre-forward and it was his presence at a corner which presented the visitors with a late chance but Ben Tozer somehow managed to scoop the ball over from inside the six-yard box.
Cambridge: Dunn; Tait, Hughes, Coulson, Taylor; Simpson, Champion, Naylor, Donaldson; Cunnington, Appiah
Subs: Chadwick (for Donaldson 46), Bird (for Cunnington 65), Taylor (for Naylor 74)
Not used: Norris, Lanzoni, Hurst, Foy
Northampton: Archer; Tozer, Cresswell, Collins, Newey; Hackett, Murdoch, Byrom, Mohamed; Richards, Toney
Subs: Robertson (for Newey 30), O’Toole (for Hackett 56), Sinclair (for Byrom 84)
Not used: Duke, Carter, Langmead, Nicholls