Cobblers' hopes of avoiding relegation this season suffered a potentially fatal setback on Saturday when beaten 2-0 by fellow strugglers Fleetwood Town on a sun-kissed afternoon at the Highbury Stadium.
Fleetwood had the worst home record in the entire division going into this game having not triumphed at the Highbury Stadium since late October, but that dismal run was ended with this crucial - and relatively straightforward - victory as Northampton lost their unbeaten away start to 2018.
Town were the better team for much of a disjointed first-half but Fleetwood held the lead at half-time through the only moment of real quality as Kyle Dempsey finished off a crisp move on 18 minutes.
The visitors looked like they meant business in a vibrant start to the second-half but once again it was a lack of fluency, cohesion and creativity in attack that was their undoing, and Cian Bolger's late second confirmed defeat, extending their winless streak to six games.
With time and games fast running out, the Cobblers are now in a seriously perilous position at the bottom of Sky Bet League One table, occupying the final relegation place and now further adrift of teams above them having also played more than anyone around them.
After successfully switching formations for Tuesday's draw against Shrewsbury Town, manager Jimmy Floyd Hasselbaink persisted with 3-5-2 for this visit to the north west and made only one alteration.
That change was enforced due to John-Joe O'Toole starting his three-game suspension with Shaun McWilliams coming in for his first start since New Year's Day as a straight swap in central midfield.
The game took a while to get going but Northampton made a steady start and edged a scrappy first quarter as they found plenty of space in promising areas of the pitch without posing too much of a threat on the home goal.
The opening goal came both against the run of play and out of character with the game itself when, on 18 minutes, Fleetwood pulled Town's defence apart with a slick move as Toumani Diagouraga and Conor McAleny combined to tee up Dempsey, who found the bottom corner with ease.
The Cobblers continued to shade the general play but their lack of cutting edge was all too apparent and it took until 40 minutes for them to turn their possession into a genuine chance, and when it arrived through Hildebero Pereira's terrific work on the right-wing, Kevin van Veen skied his first-time shot over from 12 yards.
Up the other end, Fleetwood's goal was the only time they looked remotely threatening, aside from Ashley Eastham's header from a free-kick, but it was enough to take them into half-time with a slender advantage.
Town were agonisingly close to wiping out the deficit within two minutes of the restart as more fine play by Pereira, who won the ball in midfield and then drove forward, culminated in van Veen's cross-shot only needing a touch to be diverted into the net, but it somehow eluded everyone.
Kevin Luckassen, on as a half-time change, then appeared to block from his own team-mate when Ash Taylor met Matt Grimes' corner as Northampton continued their fast start to the second period.
A rare Fleetwood attack almost saw them add a second as Dempsey's curler from range had Richard O'Donnell scrambling across his goal before Gboly Ariyibi and Chris Long were both thrown on by Hasselbaink.
But in truth his side's bright start to the half had dramatically fizzled out and Fleetwood had the game back under control, using every trick in the book to manage the game and run the clock down.
Aside from the fleeting moment of promise, Northampton barely managed an attack of note in the final quarter of the game, and another forgettable afternoon was sealed eight minutes from full-time.
Seconds after O'Donnell had superbly kept out Jordy Hiwula, Fleetwood doubled their advantage thanks to Cian Bolger's messy finish after Town again failed to clear, and that was that, with the full-time whistle greeted by a chorus of boos from the away end.
Fleetwood: Cairns; Coyle, Pond (c), Eastham, Bolger, Hunter; Dempsey, Sowerby (Glendon 88), Diagouraga; McAleny (Grant 66), Madden (Hiwula 81)
Subs: Neal, Burns, Jones, Biggins.
Cobblers: O'Donnell, Moloney, Taylor (c), Turnbull, Facey, Bunney, Grimes, McWilliams (Ariyibi 70), Pereira, Mathis (Luckassen 45), van Veen (Long 79)
Subs not used: Cornell, Barnett, Foley Hoskins
Referee: Rob Lewis