Jon Brady admitted he was “deeply hurt” after his Northampton side were relegated to League Two.
Northampton’s fate was sealed by a 3-0 defeat to Blackpool as Luke Garbutt drilled in after 19 minutes before Jerry Yates grabbed a late brace.
Brady, who has been in interim charge since February, gave an emotional post-match interview afterwards.
He said: “I’m deeply hurt by today now that we have been relegated, because I honestly believed from the outset that we could do it and I never gave up believing.
“It’s been very personal for me because we’re local and we threw everything at it.
“It hurts a lot at the moment and it’s very raw and it’ll take a bit of time to get over this.
“But in football you’ve got to pick yourself up, dust yourself down and look to put a marker down at Sunderland next weekend to say that this club won’t lie down.”
On the game itself, Brady added: “We started well and it could have been a different story because we had two penalty shouts in the first five minutes – Peter Kioso was grappled to the floor and Ryan Watson was tripped over but the referee hasn’t seen either of them.
“Alex Jones then isn’t strong enough, they go on the counter-attack and the boy shouldn’t be able to score from that angle. The second one is a fumble and then there’s the third one late on.
“They’ve invested well and they’re a class outfit but I felt we were really in the game up until half-time.”
Blackpool now just need a point to secure a play-off place.
Seasiders boss Neil Critchley said: “It was comfortable in the end but before we got the second goal it was anything but.
“I thought Northampton started very well and we thought they would because they had nothing to lose.
“The way they play makes it difficult for you because they get the ball forward early, they turn you and they force you keep the ball up the pitch.
“They pick off second balls and the pitch was difficult as well so it was very tough for us, especially in the first part of the game, but the goal came at a good time for us.
“We had a big chance just before half-time, which we missed, and when it’s only 1-0 at half-time, all it takes is a long ball or a set-piece to change the game.
“But we defended brilliantly well and the second goal deflates them and gives us a lift and then we have obviously gone on to win the game convincingly, but I don’t think that tells the whole story.”