Reeco Hackett scored twice as Pompey thrashed Southampton in a south coast derby to reach round three of the Hampshire Cup.
Zak Swanson had earlier opened the scoring, while Michael Jacobs was also on target to delight the noisy Fratton End.
Olly Lancashire was sent off for a foul on Joe Pigott in the second half, although Jimmy-Jay Morgan was still able to net twice for the visitors and give the scoreline a more respectable look.
But it was the Blues who had the final say right at the death, when academy youngster Koby Mottoh came off the bench to net their fifth.
Danny Cowley fielded those fringe players who needed minutes, as well as academy youngsters Josh Dockerill and Adam Payce.
And it was a young player who broke the deadlock on six minutes, with SWANSON drilling the ball into the bottom corner after being found in space by Jacobs.
The visitors were showcasing some neat build-up play, but struggling to properly test Josh Oluwayemi between the sticks
It was the Blues looking more likely to add to the scoring and Hackett’s effort was deflected over at the end of a neat passing move.
But HACKETT did double the lead, making no mistake inside the box when Southampton failed to deal with the resulting corner.
The visitors had a chance at the other end when Jay Mingi conceded a free-kick, but Samuel Bellis fired his effort straight into the wall.
Pompey were looking far more clinical, though, and JACOBS added a third goal for the home side on 37 minutes.
His shot was deflected into the net after Joe Pigott had done well to just about keep Swanson’s cross in play.
Half Time: Pompey 3 Southampton 0
There was drama early in the second half when Pigott looked to race onto Dockerill’s long clearance and was hauled down by Lancashire on the edge of the box.
The striker would have been through on goal and referee Gary Parsons had no choice but to brandish a red card to the experienced defender.
Pompey tried to immediately make the most of their numeric advantage, but Oliver Wright got down to deal with Jacobs’ free-kick.
The home faithful did not have long to wait for another goal, however, as Mingi found Pigott and his teasing delivery was turned home by HACKETT.
But Southampton then hit back to reduce their deficit, as Morgan raced clear and lifted a neat finish over Oluwayemi.
Morgan provided a further lift for the visitors, by rising highest to glance home Jack Turner’s corner.
The game had lacked some of the fire usually associated with a derby, but that changed when a melee broke out in front of the empty North Stand.
It quickly died down, though, and Parsons limited his bookings to one for each team, with Bellis and Swanson having their names taken.
Pompey were still perhaps guilty of some complacency and it took a decent Oluwayemi stop to deny Dominic Ballard on 66 minutes.
The hosts looked to collect themselves again and it soon took a superb save to deny Hackett a hat-trick.
He had turned Denver Hume’s delivery towards the top corner, only for Wright to fling himself to the left and turn the ball over.
Brian Quarm, Mottoh and Harbvey Laidlaw were all given chances to impress in the closing stages, replacing Dockerill, Payce and Jacobs.
Hackett was still looking to complete his treble and saw the ball ricochet agonisingly past the post after turning the Southampton defence inside out.
Pompey were firing again and when Pigott found Mottoh at the back post, the teenager’s close-range effort came back off the woodwork.
And the hosts kept possession well in the closing stages to frustrate their opponents before wrapping things up in stoppage-time.
Hume sent the ball into the box from wide on the left and MOTTOH arrived at the back post to slam it home.
Pompey (4-4-2): Oluwayemi; Swanson, Dockerill (Quarm 70), Freeman, Hume; Payce (Mottoh 77), Tunnicliffe, Mingi (c) (Murray 90+2), Jacobs (Laidlaw 82); Hackett, Pigott
Goals: Swanson 6, Hackett 30, 50, Jacobs 37, Mottoh 90+3
Booked: Mingi, Swanson
Sub not used: Osei-Owusu
Southampton (4-2-3-1): Wright; Finnigan, Lancashire, Armitage, Payne; Turner (c), Bragg (Dibling 77); Amo-Ameyaw (Doyle 55), Morgan (Charles 77 (Merry 85)), Bellis; Ballard
Goals: Morgan 53, 59
Sent off: Lancashire
Booked: Finnigan, Bellis
Sub not used: Hall
Referee: Gary Parsons
Attendance: 2,542 (285 away fans)