It was a nightmare start for Spartans as Calum Stead scored within the first minute after a defensive mix-up, before Robbie Dale equalised with a deflected free-kick to level the scores on 20 minutes.
Jordan Crawford scored what proved to be the winner just five minutes before the break with a deflected shot.
Afterwards, manager Terry Mitchell said: “I was bitterly disappointed with the result.
"We got off to a very poor start, conceding so early in the game, but we didn’t allow that to make us change our style.
“We deservedly got back into the game through Robbie (Dale). We then had a few good chances when we might have scored but our finishing just wasn’t there.
"Then Kettering went up the field and scored again just before the break with another deflected goal, which I thought was a bit harsh on us to go in 2-1 down at half time.”
“The loss f the early goal was a blow, but we have some good footballers here, and the loss of one goal doesn’t change the way we want to play the game.
"I made a few changes from the Gateshead game, but we need to keep freshening the squad up, although we always want to put out as strong a side as we possibly can.”
JJ O’Donnell added: “It was another tough day, but ultimately we just weren’t good enough. They came with a game plan and we needed to try and break that down, which we didn’t do.
"As players we have to take responsibility for that because we are out on the pitch and are the only people who can affect that.
"It was a mistake which led to us losing the first goal, but we have to show character and rise above that.
"During the game we had chances but we just couldn’t take them. In a situation like that it is important not to lose.”
On Saturday Blyth go to Guisley in what is being labelled a typical ‘six-pointer,’ and O’Donnell says they have to try and get a result to stop themselves being drawn back into the relegation zone.