What unfolded was several rising to the challenge superbly, finally posing realistic competition to a first-team which has become far too comfortable.
Intriguingly, leading the way was the much-maligned George Hirst to at last stake a claim to the problematic centre-forward role.
To put it bluntly, John Marquis has been playing by default for the Blues this season, such has been the lack of pressure applied by rivals.
Hirst was already man of the match when the Papa John’s Trophy encounter against Crystal Palace Under-21s entered stoppage time. Fittingly, he would fire Pompey into the next round.
With the Blues leading 2-0, they required one more goal to qualify from the group section – and the finish was applied in two minutes of time added on by the Leicester City man.
Certainly the loanee had a point to prove in just his third Blues start and was a powerful presence all night, presenting a calibre of striking performance rarely witnessed this season, albeit against an under-21 side.
Earlier keeper Owen Goodman produced one stunning save to deny him and another good one in the second half.
There was also a horrible effort with the outside of his right boot after excellent approach play from Hirst – but he finally found a way through in stoppage time.
Overall, it was a heartening outing from the 22-year-old, accompanied by impressive turns from Gassan Ahadme and Michael Jacobs.
Ahadme’s second-half header opened his goal account for the club, with Miguel Azeez grabbing the other in his fourth appearance.
Meanwhile, Cowley granted debuts to Academy pair Harvey Hughes and Adam Payce, with the latter handed his bow at 17 years and 20 days.
The duo put in strong displays, as did Pompey as a whole, and suddenly the likes of Hirst and Jacobs have put themselves in contention for Wycombe on Saturday.
That outcome is just as much to savour as the 3-0 win which ensures qualification from the group stages and into the knock-out rounds courtesy of goals scored.
Hughes and Payce were the only youngsters in an otherwise strong Pompey line-up featuring a number of first-team regulars.
Sean Raggett, Connor Ogilvie and Miguel Azeez kept their spots from Saturday’s unsatisfactory FA Cup win over Harrow Borough.
Elsewhere, there were rare starting opportunities for Gassan Ahadme, George Hirst and Michael Jacobs.
They were supplemented by Kieron Freeman, Louis Thompson and Alex Bass, with Cowley resisting trusting in too much young talent.
The bench, however, contained seven Academy kids, including Wales under-18 international Harry Jewitt-White.
Although Haji Mnoga was missing after collecting a shin injury during the foul which saw him red carded for Bromley against Rotherham at the weekend.
Meanwhile, Paul Downing, Ellis Harrison and Liam Vincent are not yet ready to return following injury, while Clark Roberston and Ryan Tunnicliffe remain sidelined.
When the game kicked off, on seven minutes Freeman was caught in possession inside his penalty area and a dangerous cross-cum-shot was deflected behind for the game’s first corner.
On 14 minutes, Hughes’ left-footed clearance was flicked on by Ahadme, sending Hirst racing clear to bear down on goal.
He then cut inside to create shooting room for himself, only to prefer a shot with the outside of his right foot rather than using his left.
The outcome was the ball horribly screwing away from goal when the build-up deserved so much more - and didn’t Hirst know it.
Hughes did force the Palace keeper into a save when a first-time shot from around 20-yards was met with a scrambling stop from Owen Goodman.
The ball squirmed out of his grasp for a right-wing corner which didn’t amount to anything.
Pompey were beginning to threaten and, on 24 minutes, Hirst was denied by a wonder save from Goodman
Ahadme’s shot was blocked, with the ball falling to Hirst, who struck a fierce low attempt which appeared destined for the net until the keeper flung himself to his right.
It was a stunning stop, somehow keeping the shot out, leaving the Leicester loanee with his hands on his head in disbelief.
On 29 minutes, Azeez’s corner from the right was met with a header from Hirst which was clearly on-target, only to be deflected for a corner.
The deadlock was broken on 32 minutes through a lovely finish from Azeez.
Hirst fed Ahadme inside the box, who beat the offside flag, but was unable to get into a shooting position so laid it inside to the Arsenal loanee.
Azeez controlled it with his left foot before clipping a lovely right-footed finish high into the far corner of the net.
Pompey were firmly in control and Jacobs popped up on the left-hand side in the box, only to drive an angled right-footed shot straight at the keeper.
Palace got the ball into the Blues’ net on 40 minutes when Rob Street curled a shot into the far corner for a quality finish - only for the off-side flag to intervene.
Pompey made a change at the break, with Harry Jewitt-White replacing Louis Thompson in the centre of midfield.
That took Pompey’s tally to three teenages, although it was 30-year-old Jacobs who had the first attempt of the second half, his shot straight into the arms of Goodman.
Then Hirst picked up the ball centally and drove inside before drilling a right-footed shot agonisingly past the post.
On 54 minutes, Hirst won a free-kick down the right, with Azeez touching the dead ball to Freeman, who put it into the box.
There was Ahadme with an excellent header, planting it into the top corner to make it 2-0 to the hosts.
Palace made their first change on 57 minutes, with Jack Roles replaced by James Taylor.
On 73 minutes, Jacobs’ corner from the right was met with a Hirst header which the keeper instinctively kept out on the goal line – and the striker was thwarted again.
Palace came close to reducing the deficit on 85 minutes with Malachi Boateng crashed a swerving right-footed shot against the far post.
In five minutes of stoppage time, Hirst fired in a shot which deflected for a corner.
That was delivered from the right by Azeez, flicked on by Ahadme, and there was the Leicester man in the thick of it, prodding the ball home for the winner – and Pompey are into the next round.
A message from the Editor, Mark Waldron
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