There's little doubt Hart would have told the men culpable for the gaffes exactly what their lapses have cost Pompey. Hopefully, with some serious hairdryer treatment.
This was a monumental opportunity missed, and the fact the Blues had put thems
elves exactly where they needed to be to deliver a big, big win makes it even more galling.
A textbook first-half away performance left Blackburn teetering on the brink of meltdown as a chorus of boos greeted the home side as they slunked off at the interval.
But Sam Allardyce's men climbed off the canvas and then blew the visitors away after the break with a performance of attacking might.
This, however, wasn't just about Rovers' quality on the front foot as their manager changed the game with the joint introduction of Benni McCarthy and two-goal Jason Roberts.
This was Pompey, as Jamie O'Hara put it, shooting themselves in the foot with a defensive performance so meek it was impossible for the home side not to take advantage.
Yes, Blackburn powered forward with the force of a David Haye haymaker, but Pompey showed the punch resistance of a wet paper bag.
Hart had instilled a miserly air to his defence in recent weeks, as the Blues cut out the individual errors which had marred their struggling start to the season.
They returned with a vengeance as the bleak Lancashire rained poured down at Ewood Park.
Anthony Vanden Borre, Tal Ben Haim and Frederic Piquionne have to put their hands up and accept the blame for the role they played in Blackburn's goals.
Hart came as close as he is ever going to go to pointing the finger of blame at his two full-backs, by clearing central pairing Marc Wilson and Younes Kaboul of any fault in the chaos which reigned.
It was infuriating to see the team perform so shakily as a defensive unit after eradicating the mistakes with three clean sheets on the bounce and four in five games.
And all this after they had given themselves the chance to gain a stranglehold on the game.
Pompey laid the foundations to climb out of the bottom three, then allowed the house to come down on them.
It's not as if what Blackburn came up with was of any surprise, either.
Hart would have drilled his team incessantly in training last week to deal with the threat they offered from set-pieces.
They then allowed themselves to be undone by a gut-wrenching hat-trick of goals from exactly that.
Piquionne's half-baked efforts to deal with Roberts turning and prodding a shot past David James after 53 minutes when Ryan Nelsen got the jump on Ben Haim was the start of Pompey's downfall.
That was bad enough, but a marking horror show unfolded 20 minutes later for the Blackburn skipper's decisive header.
There is a Nelson with Portsmouth links who expects every man to do his duty.
Ben Haim certainly wasn't as he allowed the Rovers captain the freedom of the visitors' penalty area to head home.
It was no secret the defender was going to be dangerous at set-pieces, but the Israel international wasn't in a Blackburn postcode as he grabbed the winner.
The third goal was poor with the otherwise impressive Vanden Borre not at the races as McCarthy was left unmarked coming out from a corner.
His cross allowed Roberts to fire home as the Blues back line came out in instalments, but the whole dynamic of the match had changed by then.
Pompey were being forced to chase a game they could have seen out to at least a result which would have temporarily pulled them off the bottom.
A modicum of defensive nous, resilience and organisation would have done the trick.
Instead it was an error-riddled capitulation, which left Hart and 600 travelling fans exasperated.
It had all started so well, too.
Okay, it wasn't a vintage first-half display but Pompey competed, got about the home side and carved out opportunities.
Aruna Dindane was proving such a nuisance that Rovers resorted to kicking lumps out of the Ivory Coast international in an effort to tame him.
He was the architect of the goal which put Pompey in front after 16 minutes.
There was still an awful lot to do, though, as he fed the lively O'Hara who took aim from 30 yards and beat his former Spurs team-mate Paul Robinson with a daisy-cutter.
Pompey will look to referee Andre Marriner allowing Pascal Chimbonda to stay on just before the break as a seminal moment in the game.
The French international clearly aimed a punch in the direction of O'Hara, pictured right celebrating his goal, as the pair tussled.
It wasn't exactly the Haye effort which rocked Nikolai Valuev in the 12th round in Germany, but the expectancy was to see the red card come out.
Marriner must have had enough of being in the headlines of late, because the man who has dished out more dismissals than any other ref this season opted for yellow.
It could, and probably would, have been a different game had he walked but there was still no excuse for the way Pompey wilted after the break as Sam Allardyce threw on McCarthy and Roberts, and went for broke with a 4-3-3.
James looked to be on his way to celebrating becoming the first Premier League player to chalk up 50,000 minutes of action – he did so after 39 minutes – with a clean sheet.
That soon changed in the space of 33 barmy minutes from the men in front of him, though.
O'Hara's assertion that one or two of his team-mates weren't ready for what they faced from Blackburn was an interesting one. They better be now because more of the same is up next against Stoke.
Pompey have been unfortunate in defeat on a number of occasions this season.
They couldn't argue that was so here. A deflated Hart didn't try to suggest that was the case in his post-match press conference.
Instead, at one stage, he was left speechless. We knew where he was coming from.
