Pompey suffered a defensive implosion as Blackpool inflicted a worrying defeat on Paul Cook’s side.
The Blues headed to the Tangerines seeking a result to build on their impressive Fratton Park form.
Instead, the travelling faithful witnessed a ramshackle performance from the visiting rearguard which was deservedly punished by the hosts.
All three of the hosts’ goals in their 3-1 triumph were handed over courtesy of poor defending or players criminally caught in possession in dangerous situations.
Certainly, it was uncharacteristic from Cook’s side, who looked a shadow of the side who were so ruthless against Barnet at the weekend.
But while they struggled to fire as an attacking force, at the back lay the real concerns as the Kyle Vassell-inspired home side tore them apart time and time again.
In particular, Pompey were susceptible to the counter-attack – Blackpool’s goal haul was all of the visitors’ making.
Kelvin Mellor headed Gary Bowyer’s side into the lead after David Forde didn’t collect a high free-kick – although Conor Chaplin levelled matters soon afterwards with a stunning overhead-kick.
It was another magnificent goal from the youngster, his third of the season arriving against the run of play to ensure it was 1-1 at the break.
However, in the second half Brad Potts tapped home after Danny Rose had been caught in possession, and Vassell wrapped it up after taking the ball off last-man Tom Davies.
A thoroughly-deserved win for the Tangerines in their sparsely-populated Bloomfield Road stadium – and for the Blues, some serious questions have to be asked about their defensive ability.
Unsurprisingly, Cook’s side was unchanged from that who destroyed Barnet 5-1 at Fratton Park on Saturday.
That meant Chaplin retaining his place up front, while Kal Naismith was again preferred to Kyle Bennett and Milan Lalkovic on the left-hand side of the attacking midfield three.
The bench was also untouched, with Michael Smith and Curtis Main the two strikers, alongside the creativity of Bennett and Lalkovic.
Noel Hunt remains sidelined with a groin problem, while Ben Close and Drew Talbot are still both out with hamstrings.
Meanwhile, fit-again Jack Whatmough is scheduled to start for the reserves at Norwich tomorrow evening.
Blackpool’s bench included Jamille Matt – the scourge of Pompey while on Plymouth’s books in last year’s two-legged play-offs semi-final.
The Blues began brightly and Carl Baker clipped in a cross from the right which was met by the head of Gary Roberts. However, the midfielder failed to get any power behind it.
Michael Doyle then drove in a left-foot shot from long range which was comfortably dealt with by keeper Dean Lyness.
On seven minutes, great vision from Naismith saw him delicately place a left-foot shot from outside the box goalwards – but it flew narrowly wide of the post.
Baker provided Pompey’s next attempt on goal, firing in a ferocious left-foot effort from long range which went close, much to his obvious agony.
The hosts won the game’s first corner when, on 15 minutes, Christian Burgess stepped across to clear Vassell’s low cross from the left, yet it amounted to nothing.
But Blackpool took the lead on 18 minutes completely against the run of play.
Potts fired in a deep free-kick from the left and Mellor got his head to the ball ahead of Forde’s fist to break the deadlock.
The goal knocked the Blues completely out of their stride and their play became ragged as they failed to retain possession.
However, on 26 minutes Enda Stevens drove in a cross from the left which Clark Robertson slid in to put out for a corner, with Chaplin lurking behind for what would have been a tap-in.
The post denied the home side extending their lead on 28 minutes, with Vassell cutting across the edge of the area before firing a left-foot shot against the woodwork.
There was another scare moments later when Armand Gnanduillet muscled his way through tackles from Davies and Burgess to find himself clean through.
But Doyle had tracked back to nick the ball off the striker’s toe and calmly defused the danger.
Yet on 34 minutes Pompey found themselves level, with another wonderful Chaplin goal.
Roberts started off the danger, tricking his way down the left and delivering a cross which eventually found its way to Rose.
When the midfielder’s shot was blocked, the ball flew up into the air, and upon its descent it was met with a spectacular overhead-kick from 12 yards out from Chaplin to level.
The match was wide open and on 39 minutes the hosts hit on the counter-attack.
Vassell crossed for Potts, whose right-foot shot from outside the box was straight at Forde.
It was all-square at the half-time whistle and at the interval Robertson was replaced by Will Aimson.
On 47 minutes, Naismith’s free-kick was deflected for a Blues corner – and a decent delivery from Roberts narrowly missed finding the head of Davies at the far post.
But moments later Blackpool had regained the lead, after Rose had initially been caught in possession.
Vassell then whipped in a cross from the left which Forde got his fingertips to, only for Potts to follow up at the far post to tap home.
The visitors responded with Stevens putting a deep cross into the far post and Roberts’ header was scrambled away for a corner.
Baker then won a foul 25 yards out. But Naismith’s free-kick flicked off the wall to drift narrowly wide with the keeper struggling.
However, the hosts extended their lead on 65 minutes when Doyle played the ball back to last-man Davies.
He was then dispossessed by Vassell, before the striker produced a composed finish.
Cook made his first substitution on 67 minutes, with the ineffective Baker replaced by Bennett. As a result, Naismith switched to the right wing.
On 78 minutes, Smith came on for Stevens, and minutes later drove in a shot from the edge of the area which was absent of power and straight at the keeper.
Forde had a reprieve when he challenged Vassell as the striker bore down on goal, flooring his opponent.
The linesman flagged for a foul, but referee David Webb overruled and saw nothing wrong.
A let-off for the visitors – yet there was no avoiding the scoreline as it finished in a 3-1 defeat.