Chris Wilder was once again left to rue his side’s defensive frailty as the Cobblers conceded a goal eight minutes into time added on to suffer a disappointing 3-2 defeat at the hands of Wycombe Wanderers at Sixfields.
Town had fought back from being 2-0 down to tie the match up at 2-2 thanks to a Sam Wood own goal and an 86th-minute header from Ryan Cresswell.
But Wilder’s men were once again left empty-handed as Alfie Mawson fired home a brilliant shot into the top corner in the dying seconds.
The result means the Cobblers end the season in 12th place in Sky Bet League Two as both Exeter City and Morecambe won to leapfrog them.
And Wilder said: “You end up where you deserve to end up, and we didn’t deserve to end up any higher so we have to accept that.
“It was better than last year, but we have a lot of improving to do in the summer.
“I have a lot of work to do, and we have a lot of work to do on the training pitch because that game today is another in a catalogue of games that we have seen up and down the country all season.
“I keep using the phrase tee to green when talking about us, because between both boxes we play quite well, and apart from a 10-minute spell in the first half we tried to drive the game on.
“But we gave silly fouls away, have not defended well at two or three set-pieces and the ball ends up in the back of our net.
“We have scored enough goals this season, we are positive when we go forward and we create, and I don’t think the defensive situation and problem is an organisational thing, it’s about mentality.
“It’s the mentality to stick your head on it when you are a centre-half, to react first to a second ball and to do what you have to do to keep the ball out of the back of the net, and we haven’t done that enough.
“That game sums us up really, we are going for a winner, but we give a daft foul away, they put the big centre-half up the top, the ball bounces to somebody, and somebody smashes it into the top corner and we all walk away from today’s proceedings really disappointed.”
And Wilder added: “It is difficult because we were chasing the game and we shouldn’t have needed to.
“We were the better side in a tight game in the first half, should have come in at half-time 0-0, but we are 2-0 down and having to chase the game as we do all the time, which makes it really difficult.”
Wycombe’s win was not enough to lift them into the top three, as Bury won 1-0 at Tranmere Rovers to claim the final automatic promotion place on offer, with Southend United losing 3-1 at Morecambe.
Burton Albion were crowned league two champions as they won 3-2 at Cambridge United and rivals Shrewsbury Town lost 2-0 at home to Plymouth Argyle, who now meet Wycombe in the play-offs.