Alfie Mawson’s goal in the eighth minute of time added on secured a dramatic 3-2 win for Wycombe Wanderers as the Cobblers ended their season on a losing note at Sixfields.
Town looked to have rescued a share of the spoils as they fought back from 2-0 down to level it up at 2-2 thanks to a Sam Wood own goal and an 86th-minute Ryan Cresswell header.
But in the dying seconds, Mawson smashed home an unstoppable left-footed shot from the edge of penalty area to clinch the three points for the Chairboys, who had scored twice in the space of four first-half minutes through Aaron Holloway and Nico Yennaris.
Mawson’s shot proved to be the last kick of the match, but wasn’t enough to secure Wycombe a place in the top three as Bury were 1-0 winners at Tranmere Rovers to claim the final automatic promotion spot.
The Cobblers made three changes to the team that started the 3-1 defeat at Burton, with two of them enforced.
Lee Collins and Brendan Moloney were both ruled out through injury, with Diego De Girolamo dropped to the bench.
Into the team came Cresswell, John-Joe O’Toole and Marc Richards, for his first start since February, with Taylor lining up at right-back and O’Toole going into central midfield.
After a scrappy opening, the first real chance was carved out after 15 minutes, and it was a lovely move by the Cobblers.
Ricky Holmes played a peach of a pass down the line and behind the full-back for Richards to run on to.
The striker laid a square ball into Ivan Toney on the edge of the penalty area and he dummied for the onrushing Lawson D’Ath, but the youngster’s finish from 18 yards lacked power and goalkeeper Matt Ingram gathered easily.
Wycombe had barely threatened, but on 20 minutes they went close with striker Paul Hayes pinching the ball off O’Toole’s toe in the Cobblers penalty area, but his looping snapshot hit the top of the crossbar with Shwan Jalal beaten.
There was plenty of commitment on show from both sides but few chances, although that changed on the 35-minute mark as Wycombe took the lead though Holloway.
The Cobblers struggled to clear a ball inside their own box, and after a bit of head tennis, the ball fell to Holloway 15 yards out and he smashed home a right-foot volley.
Town were stunned, and it got worse four minutes later when Wycombe scored again.
There was a handball from Hayes in the centre circle in the build up, but it wasn’t spotted, and in a flash Yennaris was racing on to a ball down the right wing from Mawson, having beaten Town’s high offside line.
The Wycombe winger kept his cool with a chasing Evan Horwood breathing down his neck, got into the penalty area and sent a low angled drive across Jalal and into the bottom corner of the net.
As has been the case with so many goals conceded by the Cobblers this season, it was sloppy defending, with Wycombe getting in too easy.
Town tried to respond and Richards had a header saved by Ingram, but Wycombe were only denied a third by the linesman’s flag, and that looked a tight call.
The Cobblers started the second half brightly and on 48 minutes Ingam had to be alert to palm away a shot from D’Ath after great work down the right by Joel Byrom, but again it was straight at the Wycombe goalkeeper.
Town had clearly been given a rocket at the interval and they went close again on 50 minutes, Byrom being teed up in the box by a Holmes lay-off, and his stinging shot was saved by a combination of the left hand of Ingram and defender Aaron Pierre just behind him.
The Cobblers’ early second-half fire soon blew out though, although they were gifted a way back into the game on 67 minutes.
Toney’s left-wing cross was a teasing one but was also heading straight into the arms of goalkeeper Ingram, at least it was until Wood inexplicably decided to try and cut it out, and only succeeded in diverting the ball into his own net.
To rub salt into the wounds for the visitors, Wood also managed to injure his own goalkeeper in the collision, with Ingram having to limp off and be replaced by Alex Lynch.
Wycombe responded to the setback well and Jalal did well to tip a towering Mawson header over the bar.
The Cobblers were working hard to get the leveller, and their effort was rewarded on 86 minutes with a goal from the route one handbook.
A long throw from the left wing from Jason Taylor found the head of Cresswell and his glancing backwards header looped into the far corner of the net.
With their tails up, the Cobblers pressed for an unlikely winner and substitute Darren Carter and Richards had efforts blocked, but there was still to be a dramatic finale at the other end of the pitch with Mawson’s late, late winner.
Northampton Town: Jalal, Taylor, Cresswell, Diamond, Horwood, Holmes, O’Toole, Byrom, D’Ath, Toney, Richards. Subs: Duke, Carter, Hackett, Gray, De Girolamo, Warburton, Clifton
Wycombe Wanderers: Ingram, Yennaris, Pierre, Bean, Hayes, Wood, Craig, Murphy, Holloway, Mawson, Ephraim. Subs: Jacobson, Bloomfield, Fletcher, Lynch, Kretzschmar, Onyedinma
Referee: Charles Breakspear
Attendance: 5,723 (Wycombe fans 916)