But the parallel fates of the two clubs in the meantime has seen one of the most remarkable swings in the history of English football.
When Portsmouth beat Saints 4-1 at St Mary’s in a fifth round tie, the men from Fratton Park were still a Premier League team.
Saints, on the other hand, were midtable in League One, the third tier of English football.
Though Pompey had dropped to the bottom of the top flight table, their extra class told on the day.
Few fans of either club could have foreseen how different life would be just three short years later.
On that St Mary’s afternoon Portsmouth were 34 places above Saints in the English football pyramid.
But as the fates of the two clubs have taken entirely different directions, Saints now find themselves an incredible 52 places above Pompey.
That is a total swing of 86 places – almost the equivalent of the entire top four divisions.
Pompey, like Saints did, have dropped from the Premier League, through the Championship and into League One.
But with the club still in administration and second bottom of the division, Pompey face an uphill task to avoid falling into the fourth tier for the first time since 1980.
Saints arrested their decline when they exited administration thanks to the Markus Liebherr takeover.
Since that humbling FA Cup defeat they have won back-to-back promotions through League One and the Championship. They are now finding their feet in the big time.
The stats that explain the change make good reading for Saints fans but grim viewing for Pompey followers.
Saints have played 136 league games in the last three years since the Pompey FA Cup tie, winning 72, drawing 30 and losing just 34.
That gives them an overall win percentage of 52.94 per cent.
Pompey, in total contrast, have played 137, winning 36, drawing 34 and losing 67.
That gives them an overall win percentage 26.28 per cent.
Guy Whittingham has been attempting to manage a nightmare scenario this season with a transfer embargo still in place.
A crucial High Court case that could herald a supporters Trust takeover was yesterday adjourned for the fourth time.
Whittingham has had to grab players from wherever he can and has used an incredible 53 already this season.
In the last few weeks alone, Whittingham has given 11 players their first Pompey league appearance of the season – Patrick Agyemang, Frankie Sutherland, Therry Racon, Dan Butler, John Akinde, Yassin Moutaouakil, Adam Reed, Shaun Cooper, Jed Wallace, Sam Sodje, James Keene.
In contrast, Saints have used 33 players this season.
Pompey host Carlisle tomorrow where failure to win will extend their winless League 1 streak to 20 matches – just five matches off equalling the club record.
The last time the club won a league game was at home to Shrewsbury on October 20 at Fratton Park.