The Seasiders had failed to win a midweek game on the road this season prior to the fixture at Sixfields, but were able to pick up a vital three points in the race for the play-offs as they closed the gap between themselves and sixth spot.
Pennington made fully sure his attempt crossed the line, after seeing Marvin Ekpiteta denied by millimetres during the first half.
The first effort of the game came in the eighth minute, with Kieron Bowie firing a shot straight at Dan Grimshaw after shrugging off some pressure on the edge of the box.
Down the other end, Blackpool came agonisingly close to breaking the deadlock with a dangerous corner routine ahead of the half hour mark. From close-range, Ekpiteta fired an attempt against the frame of the goal, with the ball bouncing down off the crossbar. Despite claims from the Seasiders that it had crossed the line, the officials deemed it to be just short.
Following a first half of slim pickings in terms of action, the second started with a bit more life, as a shot from Jordan Rhodes into the side-netting proved to be a warning for Northampton.
Shortly after the half chance for the 15-goal man, Critchley’s side edged their way in front. A free-kick from Karamoko Dembele caused a scramble in the box, with Pennington’s persistence proving key as he forced the ball over for certain on this occasion.
Beyond that, further opportunities did prove to be scarce, as both Rhodes and substitute Matty Virtue warmed the hands of Louie Moulden with further shots, while Kyle Joseph should’ve done slightly better with an attempt as well.
Meanwhile, Northampton couldn’t see to find a way to break down a solid Seasiders defence, who remained compact until the end.
Here’s how the Seasiders performed:

1. How did Blackpool perform?
The Seasiders took on Northampton. Photo: CameraSport - Andrew Kearns

2. Dan Grimshaw- 7
Dan Grimshaw was called into action to make an early save, but other than that didn't have to do too much. Photo: CameraSport - Rich Linley

3. Matthew Pennington- 9
Matthew Pennington showed real persistence to get the ball over the line for his goal, while at the back he produced some great challenges and looked solid throughout. Photo: CameraSport - Andrew Kearns

4. Marvin Ekpiteta- 8
It was another strong display from Marvin Ekpiteta at the back. The centre will probably be left wondering how he didn't get a goal in the first half, with his shot millimetres from being over. Photo: CameraSport - Lee Parker

5. Olly Casey- 8
Olly Casey replaced James Husband off the bench at the weekend and did a great job, and it was more of the same against Northampton. Photo: CameraSport - Andrew Kearns

6. Jordan Lawrence-Gabriel- 7
It was another strong display from Jordan Lawrence-Gabriel down the right side. Photo: CameraSport - Rob Newell