Cobblers signed off 2017 with the type of performance and result they have delivered many times throughout the year as they went from 1-0 up to 3-1 down in no time at all in being beaten by Portsmouth at Fratton Park on Saturday.
For 40 minutes of this game, Northampton were more than a match for in-form Portsmouth, who had won all five of their previous home games, and even led through Chris Long's fine breakaway goal, but that's when it all went wrong.
Not only were they unable to see out the half, they somehow found themselves behind at the break thanks to clinical finishes from Matty Kennedy and Oliver Hawkins before Hawkins' second shortly after the restart made it three goals either side of half-time.
For anyone familiar with Town's struggles this season season, they would be aware that a fightback from this point was unlikely and so it turned out as, like at Doncaster four days earlier, the visitors wilted under pressure and were only saved further misery by Portsmouth's wayward finishing.
Defeat was expected given the two teams' form going into this game but the way Northampton crumbled after Portsmouth's leveller would still have been disappointing for manager Jimmy Floyd Hasselbaink, whose side are now five points away from safety ahead of the visit of leaders Wigan Athletic on New Year's Day.
There were three changes to the team that struggled at Doncaster on Boxing Day as Jimmy Floyd Hasselbaink returned to 4-3-3, recalling Lewis McGugan, Sam Hoskins and Matt Crooks, back from suspension, to the starting line-up.
Sam Foley, Shaun McWilliams and Marc Richards were the players to make way while Daniel Powell, so long plagued by a niggling hamstring injury, was back among the substitutes for the first time since November.
Despite starting well, Town were grateful to goalkeeper Matt Ingram for not finding themselves trailing with only five minutes on the clock as he stuck out an important right boot to block from Hawkins, who had been slipped through on goal by Brett Pitman.
The visitors weren't without there moments as Hoskins' ambitious lob almost caught out Luke McGee, who then beat away Matt Grimes' long-range shot, but Portsmouth were in the ascendancy and dominated possession.
They worked the ball well to create overlaps on either flank and send in dangerous crosses but Northampton were organised and worked hard to keep their hosts at arm's-length as Ben Close's shot flew over and Kennedy's effort looped just over after taking a wicked deflection.
Those were the only incidents of note prior to an explosive end to the half that saw Northampton hit the front on 36 minutes only for Pompey to respond with two quickfire goals and lead by half-time.
All three goals were of terrific quality, particularly Town's as they won the ball from deep inside their own half and launched a swift counter-attack that culminated in McGugan slipping through Long with a perfectly-weighted pass and the striker made no mistake when confronted by McGee, coolly rolling into the bottom corner.
But all of Northampton's hard work came undone in the closing five minutes of the half, with Kennedy needing only five minutes to equalise. He cut in from the left side, played a one-two on the edge of the box and drilled a first-time shot into the bottom corner to bring Portsmouth level.
Within moments of that, Hawkins, whose height and strength had been a nuisance for Town all half, then showed equal precision when getting between the away defence to latch onto Christian Burgess' long ball and send a perfectly-placed looping header over Ingram and into the same corner Kennedy had just found.
If that was bad, it gone worse just four minutes into the second-half as Portsmouth's crossing tactic finally paid off when Hawkins rose above David Buchanan at the back post to steer Dion Donohue's wicked delivery into the bottom corner.
It had taken the Cobblers just eight minutes of play to go from a position of strength to being in danger of suffering another heavy defeat as Close then smashed the crossbar and Ingram beat away Pitman's curling shot.
Ingram had suddenly become a busy man and he was straight back in the thick of action, denying Hawkins, Close and Kennedy in quick succession, while Jamal Lowe shot wide when one-on-one for the rampant hosts.
Signs of an unlikely Northampton fightback were sporadic, despite Crooks forcing McGee into a rare save, and further chances went begging for Portsmouth in a one-sided final quarter of the game, though the hosts were more than happy with three goals and three points by full-time.
Portsmouth: McGee, Thompson, Burgess, Clarke, Donohue, Rose (May 28), Close, Evans (Lowe 45), Pitman (c) (Chaplin 90), Kennedy, Hawkins
Subs not used: Bass, Main, Bennett, Casey
Cobblers: Ingram, Moloney, Taylor, Poole, Buchanan (c), Grimes, McGugan, Hoskins (Powell 64), Crooks, O'Toole (Foley 59), Long (Richards 73)
Subs not used: Cornell, Smith, McWilliams, Waters
Referee: Lee Swabey
Cobblers fans: 538