So it was again a stoppage-time goal, albeit this time in Pompey’s favour, on this occasion on the stroke of the interval.
Nonetheless, two minutes at the end of the first-half signalled a Pompey victory – and finally there was to be no heartbreaking comeback.
John Marquis supplied it, touching home substitute Brandon Haunstrup’s delightful cross which curled invitingly towards goal.
Suddenly the deadlock was broken, the glaring cracks of an abject first-half hurriedly papered over.
There were likely to be strong boos at the break, instead nothing but hearty cheers emerged, such was the dramatic effect of Marquis’ intervention at first-half death.
The lead was narrow, of course, yet, in truth, the encounter was settled as this awful Southend side destined for relegation unsurprisingly crumbled.
Following the interval, treasuring their breakthrough, it became a challenge of how many Kenny Jackett’s men would inflict upon Sol Campbell’s men.
Southend are not equipped to stage fightbacks produced by the calibre of Coventry, Bristol Rovers and Oxford United. Once their resistance had been broken apart, that was it.
And how Jackett’s men built on that first-half advantage, creating an emphatic outcome while pouring forward towards the Fratton end.
The recalled Ellis Harrison struck twice, the second a penalty, while substitute Marcus Harness also got in act for the 4-1 result.
There was a flutter of nervousness when Brandon Goodship’s shot couldn’t be kept out by Alex Bass to make it 2-1 on 69 minutes.
Yet Pompey merely resumed the offensive to ensure there was to be no late drama, not on this occasion anyway.
And the side overseen by 2008 FA Cup winners Campbell and Hermann Hreidarsson were comprehensively dispatched for the Blues’ fifth League One victory of this disappointing campaign so far.
In the build up, Bass was handed only a third Football League outing of his career following injury to Craig MacGillivray.
The Scot’s problem was described as ‘slight’, sufficient to keep him out of Southend’s visit, while ensuring a call-up for his young understudy.
That represented one of two changes to the team which were denied victory over Oxford United in such heartbreaking circumstances on Saturday.
Jackett also recalled Harrison to lead his front line, with Marquis dropping into an unfamiliar number 10 role and Gareth Evans omitted to the bench.
Also among the substitutes was fit-again Brett Pitman, who returned following the groin injury which sidelined him from the previous four fixtures.
That meant no place in the match-day 18 for James Bolton, who appeared as a sub in that 1-1 draw against Oxford at the weekend.
When the game kicked off, it took under three minutes before the hosts carved out their first attempt on goal.
Lee Brown’s deep ball from the left was headed as far as Tom Naylor, who produced a right-footed snap shot from outside the box which ricocheted off a defender for the game’s first corner.
The match was struggling to get going, however, and the next meaningful effort wasn’t until Isaac Hutchinson’s long-range attempt on 16 minutes, which Bass dived to gather.
On 25 minutes, the Blues had a great chance when Close squared the ball to Marquis following a neat build-up.
However, the striker wanted a touch and was crowded out, when a first-time shot would have been the most sensible route from such a promising position.
At the other end, it took a smart low save from Bass to deny Brandon Goodship after the striker had been put clean through, the ball then diverted for a corner.
It represented the best goal attempt of the match so far - and the young keeper deserved every credit for his intervention.
Then, on 38 minutes, Hutchinson struck a sweet shot from 25 yards which was cleanly taken by Bass without too much trouble.
In the build up to that moment, Ross McCrorie pulled up with an apparent hamstring injury in front of the South stand, prompting his substitution for Brandon Haunstrup.
With no right-back on the bench, the left-back had to operate in an unfamiliar role during the accompanying reshuffle.
Pompey had their best attempt on the stroke of half-time when Marquis fed Ben Close and his shot was tipped around the post superbly by Nathan Bishop.
Harrison back-heeled the ball to prevent it running out of play kept the moment alive, but a desperate lunge from a Southend player nicked the ball away from Close’s follow up for a corner.
The deadlock was broken during two minutes of first-half stoppage time, through Marquis.
Following a patient build up, Close slid the ball across to Haunstrup on the right, who lofted an excellent left-footed cross into the six-yard box, which was nudged past the keeper by Marquis.
The quality of the delivery meant a mere touch was needed - and Pompey headed in at the break with a 1-0 advantage.
When the match restarted, Harrison should have doubled the Blues’ advantage within three minutes.
Curtis curled in an inviting cross from the left and, unmarked and six-yards out, the striker somehow planted his head over the bar when it would have been easier to score.
Yet he did score on 50 minutes through pure persistence, crashing the ball home from the tightest of angles and close range.
It was the former Bristol Rovers who had started the move, with firstly Curtis blocked and then Williams steering a header back into the direction of the striker, who made no mistake from practically the byline.
Pompey were sensing more goals - and rightly so - and, on 55 minutes, Brown pulled the ball back from the left and Naylor galloped in and crashed a right-footed shot from 25 yards against the post.
Then Marquis’ left-footed drive from outside the box was fumbled by Bishop, but fortunately for the visitors diverted it for a corner.
There was a lifeline for Southend on 69 minutes when Goodship was allowed to drive forward and unleash a ferocious effort from outside the box.
Although straight at Bass, the keeper couldn’t keep it out, and it deflected off his hands and into the net, much to the delight of the home fans gathered behind.
On 79 minutes, Pompey earned a penalty after Sean Raggett was hauled down inside the box as he attempted to meet Curtis’ free-kick from the left.
After deliberation with Marquis, Harrison emerged with the ball to take up duties, sending the keeper the wrong way for his second of the match.
It was 4-1 on 84 minutes when substitute Marcus Harness drove in an angled finish from the right, completing the thumping scoreline and a welcome Pompey win.