From topping the table at Christmas following a 2-0 victory at Hull, the Blues’ new year implosion resulted in not even a League One play-off spot being secured after Sunday’s 1-0 defeat at Accrington.
There have been an array of reasons why Pompey, for a fourth successive season, failed to deliver a Championship return.
Following the Accy defeat, plenty of blame has been fingered at the players, while sections of supporters reckon Kenny Jackett’s dismissal was too late and didn’t leave Danny Cowley with enough time to turn things around.
But given Pompey’s commanding position at the turn of the year, not for the first time while shackled to the third tier, their January recruitment left a lot to be desired.
After uninspiring signings of previous winters such as Sylvain Deslandes, Lloyd Isgrove and James Vaughan, it was an opportunity to finally get things right this time around.
Instead, the same mistakes were repeated.
In fairness, none were bad recruits on paper – but neither were the likes of Connor Ronan, Viv Solomon-Otabor and Omar Bogle.
Yet for a fourth successive January, the fresh faces didn’t have the tangible impact to ensure Pompey consolidated at the summit.
Harvey White was the first through the door and brought with him a burgeoning reputation from Tottenham.
The midfielder displayed glimpses of his talent and has a bright future, with Pompey already enquiring for him to return for next season.
However, to think a 19-year-old experiencing his first senior loan would make a barnstorming impact was folly.
Instead, George Byers was expected to be the Championship midfielder whose quality many predicted would make the real difference.
There was a hope he'd have a Ben Thompson-like influence on in the second half of the campaign, having played 39 times for Swansea when they suffered Championship play-off semi-final defeat last term.
However, bar one magical assist in the 1-0 win over Bristol Rovers last month, Byers didn't stamp his authority at PO4.
There were a few clever passes, a couple of moments of class, but under two managers he failed to become a regular starter.
Perhaps it was harsh to bank on so much from Byers given he’d played only once for the Swans in the first half of the campaign because of an ankle injury.
When Charlie Daniels was first linked with a move to Fratton Park to replace Cam Pring, who'd returned to Bristol City, there was scarcely a fan who disapproved.
The left-back had been an established Premier League performer with Bournemouth not long ago and, by all accounts, impressed at Shrewsbury during the first half of the term.
But subbed at half-time at Bristol Rovers, in the Papa John's Trophy final and dropped after giving two penalties away despite Lee Brown being injured, it was clear Daniels' performance levels had jettisoned from his days at the Cherries.
The other recruit, Lewis Ward, was drafted in late after Alex Bass' injury.
However, there's still an argument Duncan Turnbull could have served on the bench and an emergency loan keeper could have been recruited had anything happened to Craig MacGillivray. That would have left some room in the budget.
There were also fears Pompey were a body light in the striking department. Although the squad cap prohibited a senior option coming in, an under-21 might have been worth looking at.
For example, Everton's Ellis Simms, 20, bagged eight times for Blackpool.
In contrast, the majority of the Blues' rivals recruited shrewdly in January to get them into the promotion places.
Hull brought in Dan Crowley and Gavin Whyte - on loan from Birmingham and Cardiff respectively - who ensured they sealed the League One crown.
Blackpool signed Kevin Stewart, Elliot Embelton and Simms, who helped them remarkably hurtle from mid-table to third.
Meanwhile, Jordan Jones scored three times in 20 games for Sunderland, Morgan Rogers plundered six goals for Lincoln and Elliott Lee bagged five times for Oxford.
It’s now Danny Cowley’s mission to get Pompey fighting for the Championship yet again, having been appointed head coach on a full-time basis.
Firstly, he must get their summer shopping bang right on to ensure the Blues bolt out of the 2021-22 season traps.
Should Cowley guide Pompey near the top at Christmas, then the mistakes that have occurred for four years can’t be repeated.