Goal-happy Mansfield blasted four for the second time in a week to surge into fifth place and leave pre-season promotion favourites Northampton without a win in five games.
Former Northampton striker Derek Asamoah was the star for the rampant Stags, scoring once and creating two more against the club he left in the summer.
Remarkably there were just ten survivors from the play off semi-final second leg between the two sides at Field Mill less than four months earlier.
Northampton, who won that second leg and a league match just two weeks earlier but still failed to make the play off final, created all the early chances.
Fred Murray fired a 30-yard free-kick into the defensive wall and Scott McGleish's attempted overhead kick, on the end of a darting Eric Sabin run, bobbled wide.
However the best opportunity fell to the home side in the ninth minute. Alex Baptiste's persistence won the ball and Asamoah's pass released Colin Larkin, but the striker was foiled by loan keeper Paul Rachubka - the keeper who broke Mansfield's hearts in that play-off final back in May.
But three minutes later Rachubka, making his debut on loan from Charlton, had no chance as Asamoah grabbed his third goal for the Stags.
Central defender Rhys Day's pinpoint 50-yard cross-field ball picked out Wayne Corden and his inviting left-wing cross was headed home by Asamoah.
Ashley Westwood headed a Josh Low corner wide and then Low's close-range shot was well held by the diving Kevin Pilkington, before Northampton levelled eight minutes before half-time.
The lively Sabin, a constant thorn in Mansfield's side, rose highest to nod in Mark Hughes' flick on after a period of intense pressure.
However, just six minutes later, Mansfield regained the lead. This time Asamoah turned provider, his raking 40-yard pass finding Corden who skipped past two challenges before blasting in from ten yards.
Eight minutes into the second half the pace of Asamoah unlocked the Cobblers' defence again and his final left-wing cross was guided in by Larkin.
Any hopes of a Northampton fight back disappeared in the 79th minute when Marc Richards' header was pushed up by Pilkington, celebrating his 150th appearance for the club, and then headed off the line by Day.
Four minutes from time Cordern crowned Mansfield's victory with a terrific solo goal, beating two defenders on a mazy run and crashing a 25-yard drive into the roof of the net.