Kelvin Langmead scored at both ends as the Cobblers secured a priceless late victory over 10-man Southend United at Roots Hall.
Town looked to be heading for a draw when Langmead unfortunately turned a Matthew Lund header into his own goal to cancel out Roy O’Donovan’s early strike.
The home side had responded well to losing controversial defender Bilel Mohsni to a red card for a high challenge on Chris Hackett on the half-hour mark.
But they finished the game empty-handed when Langmead headed in to seal a 2-1 win that pushes them back into the npower League Two play-off places.
Southend made the game’s initial running, Ben Tozer blocking Kevan Hurt’s shot from 16 yards in a sustained spell of early pressure but it was O’Donovan who broke the deadlock.
Town had already served notice of their intention and ability at the long Ben Tozer throw when the centre-back got a second chance to propel one into the box on 11 minutes.
Southend defender Sean Clohessy got only a glancing header on the ball in, O’Donovan intelligently followed it to the back post and hooked a shot over Paul Smith’s head that nestled in the far corner.
Mohsni’s much-predicted dramatic moment came moments before the half-hour mark in the form of a high foot on Hackett.
It was a challenge that was reckless rather than malicious and the clear harm it did Hackett was unintentional, but Mohsni did not need to make the challenge and paid the price for what was a poor piece of decision making.
Against the 10 men, O’Donovan almost doubled Northampton’s lead with a stinging shot from 15 yards that Anthony Straker did well to block before Luke Guttridge fired a volley into the upper tier of the stand behind the goal.
There was little action to speak of until Southend’s equaliser, an unfortunate own goal by Langmead, who sliced in off his left-hand post from Lund’s header at a corner.
The goal gave Southend the impetus and after it they enjoyed a long spell of possession that was punctuated by brief counter-attacks from a Cobblers side who looked at that point like they were the ones playing with 10 men.
Hurst struck a drive at Nicholls with a quarter of an hour to go that he just about parried to safety and only poor decision in key areas prevented the home side from taking a lead, although Fredy Eastwood’s shot certainly struck an arm in the box in the final 10 minutes.
But the afternoon was to end in disappointment for Southend, who probably did enough to take a point from a contest but had to ultimately settle for none.
Tozer’s throw had been repelled but only as far as Hackett, who speared in a cross that Adebayo Akinfenwa, under pressure, headed more up than across and Langmead diverted into the far corner.
Southend: Smith, Clohessy, Mohsni, Prosser, Straker, Hurst, Spillane, Lund, Mayor, Corr, Assombalonga
Subs: Eastwood (for Mayor 33), Harris (for Spillane 90+4), Reeves (for Assombalonga 90+4)
Not used: Coughlan, Bentley, Leonard, Woodyard
Cobblers: Nicholls, Johnson, Langmead, Tozer, Collins, Hackett, Harding, Guttridge, Widdowson, O’Donovan, Platt
Subs: Akinfenwa (for Collins 70), Oyeleke (for Platt 90+2)
Not used: Demontagnac, Snedker, Robinson, Hornby
Cobblers fans: 449