Two goals in four second-half minutes sent Pompey spinning to another frustrating home defeat to Stevenage.
Steven Schumacher and Matt Godden did the damage for Borough as they picked up a 2-1 success at Fratton Park.
Michael Smith’s effort 10 minutes from time set up a late charge for the Blues.
But there was to be no leveller as Jack Whatmough headed off the post deep into stoppage time.
It proved a first half where the final ball let Paul Cook’s side down in their approach work.
The fans stuck with their their team after the break, though, and the pressure was upping after Conor Chaplin’s introduction - until the familiar sucker punches arrived.
Pompey were unchanged from the team who beat Luton on Tuesday, meaning Michael Smith continued with Chaplin on the bench.
Smith just missed an early cross from Kyle Bennett, before Bennett cracked a peach of a curling shot off the post after eight minutes.
Matt Godden stung the palms of David Forde seven minutes later, with the Blues keeper gathering the ball at the second attempt.
Bennett was at the heart of Pompey’s best play and saw his header at the back post kept out by Jamie Jones’ dive to his right.
Evans’ shot from 25 yards was then blocked after 24 minutes as the Blues pushed for the opener.
But for all the pressure there was a lack of real clear chances for Cook’s side.
And there was a heart-in-mouths moment as the half wore on, as a lob over the top saw striker Matt Godden clear but a late flag went up for offside.
Pompey made two changes at the break as Michael Doyle and Christian Burgess were withdrawn for Amine Linganzi and Jack Whatmough.
Bennett was the first to test Jones eight minutes after the restart, but the Stevenage keeper kept the ball out at the second attempt.
Pompey fans were remaining with their team despite frustration growing at the lack of breakthrough.
And Cook was demonstrably showing his appreciation as his claps joined in with their chants.
Chaplin was introduced as the final sub as he replaced Bennett after 67 minutes.
And he missed a great chance three minutes later as he blazed over from six yards after good play from Roberts and Smith.
The sucker punch arrived moments later as the visitors took the lead.
Stevens lost the ball and it ricocheted to Schumacher who fired his shot through Forde’s legs.
It got worse four minutes later as Godden found space after a duffed clearance from Forde and fired home at the second attempt.
But Smith gave his team hope with 10 minutes left as he lashed a shot home at the back post from Evans’ delivery.
Roberts went close with a 20 yarder as normal time came to a close.
And sub Whatmough then agonisingly headed off the post with the last touch of the game.
That keeps Pompey in fourth place - seven points off new leaders Carlisle.