Pompey must win at Sunderland – or rely on unlikely assistance – to remain in pursuit of automatic promotion.
That is the stark scenario facing Kenny Jackett’s men, regardless of a remarkable seventh-straight League One win.
Barnsley are the team to catch, presently occupying second spot and possessing a two-point advantage.
On Saturday, Daniel Stendel’s men host a Blackpool side clutching three wins in their last 14 fixtures.
Their season ends with a trip to Bristol Rovers, the club with the second-worst home record in League One.
It would be reasonable to expect the Tykes to claim a maximum return from those remaining matches, earning a final tally of 94 points.
Pompey, with three fixtures left, can total 95 points, should victory be claimed in all of them.
The club captured the League Two title on goal difference – two years later they have the opportunity of seizing a Championship place by a single point.
However, a Stadium of Light draw on Saturday, effectively two points dropped, would ensure a maximum haul of 93.
Such an outcome would prevent both Pompey and Sunderland from overhauling Barnsley. Providing, of course, the South Yorkshire club beat both Blackpool and Bristol Rovers.
Analysing Barnsley’s forthcoming opposition does not make encouraging reading for the Fratton faithful.
Stendel’s men boast the second-best home form in League One and have won three-straight matches, following a stutter of one victory in five.
On Saturday they welcome ninth-placed Blackpool, who now cannot make the play-offs and have little motivation remaining.
Terry McPhillips’ side triumphed 2-1 over Fleetwood on Monday in a local derby.
However, they had to rely on Nathan Delfouneso’s winner four minutes into time added on – against a team reduced to 10-men following Nathan Sheron’s 72nd-minute dismissal.
Overall, Blackpool have amassed nine points from their last six fixtures.
Barnsley’s season concludes with a trip to Bristol Rovers, a team still threatened by relegation.
Monday’s 1-0 Memorial Stadium defeat to Rochdale leaves them 15th, still only four points ahead of the relegation zone.
It marked an 11th League One loss at home this season, equalling the worst return in club history.
Overall, Graham Coughlan’s side have tasted victory just once in eight fixtures, albeit arriving against rock-bottom Bradford in the last minute.
Incidentally, the Pirates have won just five of 22 home league games this season, with only AFC Wimbledon possessing an inferior record.
It adds up to win or bust for Pompey at Sunderland on Saturday.