Accrington 4 Portsmouth 1: Neil Allen's verdict - Season's worst from abysmal Blues left punch-drunk by admirable Accy

It was happy hour, The Housemartins’ finest greeted the final whistle amid the announcement proclaiming all pints were reduced to £1, a significant reduction from the standard £2.50.

It is recent custom in Accrington parts to mark victory in such a manner, and how the rejoicing support seized advantage.

Raising a glass to establishing further distance themselves from the League One relegation zone – and a successive thumping home league triumph.

The 4-1 scoreline represented Blues humiliation, certainly there could be no begrudging Stanley’s thoroughly-deserved evening of celebration.

In truth, the size of defeat should have been even more emphatic, Pompey spared added embarrassment courtesy of the post also struck twice.

Last month Bolton were dispatched 7-1 – there could well have been a crushing repeat.

Saturday was significantly the Blues’ worst performance of the campaign, an abject showing underpinned by shocking second-half capitulation.

Jackett’s men had opened the scoring against the run of play, yet their creaking makeshift defence soon crumbled alarmingly in the face of incessant attacking pressure applied by a side previously 18th in the table.

Dodging hailstones in bitterly-cold Lancashire, Pompey arrived at the Crown Ground unbeaten in 10 matches in all competitions, an impressive run to earn their boss nomination for Sky Bet’s Manager of the Month for November.

What unfolded was a pathetic showing in which few of those players participating can dredge up any positives from their performance.

This Blues side, with its automatic promotion ambition, continues to be unconvincing, irrespective of recent advancement up the table which rightly earned applause.

As ever since his Fratton Park tenancy began, Jackett’s team possess a capacity to be able to string together periods of productive results.

Last weekend’s Peterborough draw ended a run of six-successive triumphs, with defensive errors robbing them of a warranted three points to extend that winning streak.

But strip away hard-fought victories against non-leaguers Harrogate and Altrincham, plus League Two Altrincham, and this side remain suspect.

Unquestionably equipped with play-off credentials, yet, approaching the midway point of the campaign, have done little to suggest they are capable of anything more.

Certainly an effective January transfer window is required to transform a squad now reeling from left-back injuries into legitimate contenders for League One’s top-two positions.

There is mitigation for Saturday’s hammering at Accrington, of course, let there be no knee-jerk response.

A second defeat in 16 matches may have prompted a resurgence in calls for Jackett’s head across social media, but it remains an excellent sustained period of results.

Nonetheless, injuries and unavailability forced the fielding of a completely new back four at the Crown Ground, matters beyond the manager’s control.

The likes of Anton Walkes and James Bolton had previously been jettisoned from his starting XI following unsuccessful stints, now he was restoring them through desperation.

In addition, Sean Raggett was presented with his first league start since the beginning of November, with Tom Naylor dropping back from midfield to complete the improvised defensive look.

The constant overlooking of Paul Downing remains puzzling, even in times of crisis the manager would prefer utilising a central midfielder to replace a converted striker in the centre of defence.

Downing signed a three-year contract in the summer, now he finds himself fifth choice, with the impending return of Jack Whatmough set to ramp up competition further.

Still, with Lee Brown and Brandon Haunstrup injured, Christian Burgess suspended and Oli Hawkins absent following the birth of his son, a defensive overhaul was necessary, patched up and thrust into the first-team.

What unfolded was a wretched performance, not merely from the Blues defensively, with three goals in 14 minutes at one point, but a malaise spreading across the pitch culminating in such an appalling outcome.

Jackett had been forced to dip into a squad assembled with automatic promotion in mind – and they failed to step up.

Among the five changes to the team which lined-up against Peterborough, Ross McCrorie was handed his first start in his favoured midfield role since mid-September.

Replacing Naylor, who was required elsewhere, he and Ben Close made absolutely no impact in the holding areas, swamped by an Accrington side demonstrating energy in abundance and a bite alarmingly absent from the Blues’ make-up.

Naylor may possess certain limitations, admittedly, yet is pivotal to the running of the side and must remain in his most effective position rather than switched around to plug other gaps.

Never more was that apparent than against Accrington, as the midfielders in his absence chased shadows and tackled empty space.

The final change was Marcus Harness introduced for Ryan Williams on the right, a tactical decision which produced the Blues’ opener on 35 minutes.

The winger drove in a cross from the right which was met by the head of Ronan Curtis from 12-yards out for his eighth goal of the campaign.

Towering left-back Jerome Opoku had already struck the post from long range before the hosts deservedly levelled on 44 minutes, albeit in bizarre fashion.

Joe Pritchard’s right-wing flag kick was met with the head of Ellis Harrison, who thumped it into the top corner past his own goalkeeper from eight-yards out for the equaliser.

That ensured the scores were level at the break and, following the interval, Pompey did start strongly, finally beginning to impose themselves.

Then arrived the turning point on 62 minutes, when Fulham loanee Opoku surged down the left flank, shrugging off Bolton while a flailing arm accounted for Harness.

Playing the ball inside to Dion Charles, the striker fainted with his right foot and switched to his left to drive through the legs of Craig MacGillivray.

Jackett's men swiftly capitulated, moments later Pritchard’s cross from the left striking the far post after finding it’s way through the box.

Then, on 69 minutes, it was 3-1, a poor clearance presenting itself to Sam Finley, whose right-footed shot was pushed out by MacGillivray and slotted home with ease by Colby Bishop following up.

Bishop grabbed his second just seven minutes later when Jordan Clark nudged the ball out to his right and Bishop calmly placed a first-time angled shot past MacGillivray.

The scoreline was complete, followed by cheers and beers as happy hour gripped the joyous Crown Ground.

As for Pompey, they have a hangover which requires more than a night-time’s sleep to resolve – January’s transfer window will be intriguing.