Colin Cooper's side suffered a horrible 5-1 defeat on a disappointing night at Sixfields Stadium.
Pools got off to the ideal start as a lovely ball over the top from Tommy Miller found Charlie Wyke waiting to pounce.
The on-loan striker showed great composure to take the ball on into the box and slot home calmly past Jordan Archer to make it 1-0 with just 46 seconds on the clock.
Pools continued their bright start, with Wyke in particular looking a real threat with his constant pressing in the final third.
But the tide was about to turn for Pools as Stuart Parnaby tripped Kaid Mohamed inside the box and the referee was quick to award a penalty.
Marc Richards stepped up to take the spot kick and powered it into the bottom left corner of the net to make it 1-1 on 12 minutes.
The hosts worked hard to force high tempo to the game, pushing forward at every opportunity but Cooper’s men remained a threat at the other end, offering more going forward than in Saturday’s match.
Scott Flinders pulled off a great save to deny Chris Hackett from the edge of the area and then reacted quickest to clear the rebound from Lawson D’Ath.
It was then the hosts who began to enjoy the most pressure, forcing their way through the right channel with a couple of decent moves.
And their second goal came from the right as a deep cross sailed into the box and found Mohamed waiting, and he smashed the ball into the right corner of the net to make it 2-1 on 20 minutes.
A Ryan Brobbel cross opened things up at the other end for Pools but as Charlie Wyke rose to meet the ball, he was clattered by Zander Diamond.
The big striker crashed to the ground after the challenge and, after a lengthy delay for treatment, he left the field on a stretcher and was replaced by Marlon Harewood.
Pools showed a more positive response after the delay and Jonathan Franks went close with a low drive, before Jack Compton and Harewood combined to set the former through on goal. Compton’s shot flashed across the face of goal and went wide of the far post and Pools were quickly hit again at the other end.
Another Hackett cross into the box from the right found Mohamed again; this time the winger was highest as the ball arrived and his header left Flinders with no chance at the back post and it was 3-1.
Pools continued to see their fair share of the ball but once again were just lacking that final touch inside the box to beat Archer. And so Cooper’s side went into the second half with a real mountain to climb if they were to take anything from this game.
They did start the second half quite brightly, with Franks and Brobbel both working hard to create a way back for their team, but for every attack by Pools they had to face the hosts on the counter at the other end.
Scott Flinders pulled off another solid stop to deny Joel Byrom with a strike from distance as the hosts remained a real threat with every attack.
Despite Pools’ possession though, there remained little to test Archer and the hosts showed a more clinical edge – making it 4-1 on 67 minutes. More poor defending from Pools allowed Northampton forward Richards to free Hackett down the right, and Lawson D’Ath finished calmly from his early cross that was not dealt with by the visiting back line.
And things got even worse for Pools as more sloppy defending lead to the fifth goal for Northampton; again the hosts were allowed to travel forward too easily - this time down the left - and when the ball fell to Marc Richards 25 yards out, he unleashed a fierce drive that hit the back of the net and made it 5-1.
Full Time: Northampton Town 5 Pools 1
Att: 3653 (130 Pools)
Northampton Town: Archer, Alfei, Richards (O'Toole 84), Hackett (Toney 73), Diamond (Collins 41), D’Ath, Mohamed, Byrom, Watson, Cresswell.
Subs Not Used: Carter, Tozer, Snedker, Ravenhill.
Pools: Flinders, Parnaby (Richards 77), Bates, Harrison, Austin, Brobbel, Miller, Walker, Compton, Franks (Woods 88), Wyke (Harewood 28).
Subs Not Used: Woodman, Collins, Holden, Jones, Richards.