Hibernian's lacklustre defensive show left manager Pat Fenlon hugely frustrated after a thrilling 3-3 draw with St Mirren at Easter Road.
Leigh Griffiths grabbed a double as the hosts twice led and then fought back with a late equaliser to share the spoils against their struggling visitors.
Although it was a goal-feast enjoyed by the 9,000 fans, Fenlon was not so forgiving and said: "It was a nightmare. Where do I start?
"The positives. I thought we played well and our two young kids out wide, Danny Handling and Alex Harris, were different class.
"We created a lot of chances and I thought we deserved to win. But when you defend like we did today, you are not going to win games."
At the other end though, Griffiths did receive his manager's compliments after he banged in his 27th of the season.
"The first goal he scored was as good a goal you will see," Fenlon added. "He's in with a shout of winning player of the year.
"He's a special striker. He scores all sorts of goals as we saw today. He's got a bit of a habit of scoring against St Mirren so they will be glad to see the back of him I suppose."
Roy O'Donovan and Luke Guttridge hit the second-half goals to sink Edgar Davids' team who needed a final day victory to ensure League Two survival.
Barnet made a cautious start and Cobblers had two early chances with Ben Harding involved in both. The midfielder fired over before releasing Jake Robinson, who burst clear but saw Graham Stack save his weak effort.
O'Donovan was also thwarted by Stack after Mark Byrne fired Barnet's best early opening into the side-netting after neat play from Jake Hyde.
In a first half of few chances, Barnet should have broken the deadlock when Keanu Marsh-Brown beat the offside trap but shot straight at Lee Nicholls with the unmarked Luke Gambin better placed to score.
Byrne tested Nicholls with a free-kick although neither goalkeeper was seriously troubled in the first period.
Showing more urgency, Barnet twice went close in quick succession after the restart. Elliot Johnson's cross came back off the bar and Hyde's rebound was cleared off the line by Lee Collins.
But O'Donovan finally broke the deadlock in the 67th minute when he latched on to Guttridge's defence-splitting pass to beat Stack from 15 yards.
And six minutes later Guttridge doubled Northampton's advantage when he fired an angled drive past Stack after being set-up by substitute Adebayo Akinfenwa.
Barnet rallied but failed to create a serious opening that could have got them back into the contest as they saw their hopes of avoiding the drop disappear.
