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:

7. Ollie Norburn- 7
It was a solid enough night from Ollie Norburn, who was subbed off in the 72nd minute, and looked in a little bit of discomfort as he left the pitch. Photo: CameraSport - Rob Newell

8. George Byers- 7
Another display with plenty of positives from George Byers. Photo: CameraSport - Andrew Kearns

9. Hayden Coulson- 8
Hayden Coulson made a couple of dangerous runs down the left side, and did well to win the free kick that led to Pennington's goal. Photo: CameraSport - Andrew Kearns

10. Karamoko Dembele- 8
It was another busy display from Karamoko Dembele, who was involved in a lot of the good things Blackpool did. Photo: CameraSport - Andrew Kearns

11. Jordan Rhodes- 7
A couple of half chances came Jordan Rhodes' way but he was unable to do anything to trouble Louie Moulden. Photo: CameraSport - Andrew Kearns

12. Jake Beesley- 7
Jake Beesley wasn't too involved up front for the Seasiders, but once again worked hard for the Seasiders off the ball and put pressure on the Northampton keeper a number of times. Photo: CameraSport - Andrew Kearns