Pompey won at Leyton Orient to finish top of Southern Group E in the Bristol Street Motors Trophy, despite playing more than three-quarters of the game with just 10 men.
They recovered from the setback of having Sean Raggett sent off by taking the lead through Christian Saydee just before the break.
Joe Pigott came off the bench to draw the Londoners level in the second half, but Abu Kamara grabbed the winner.
The result means that as well as qualifying for the last 32 of the competition, the Blues will have a home tie in the next round.
John Mousinho made 11 changes from the side that exited the FA Cup at Chesterfield at the weekend.
There were first appearances of the season for Harry Jewitt-White – who paused his loan spell with Havant & Waterlooville – and Denver Hume.
Kusini Yengi led the line, with an attacking triumvirate of Kamara, Saydee and Gavin Whyte just behind him.
Raggett skippered the side and Ryan Schofield was stationed between the sticks, while Zak Swanson, Ryley Towler and Ben Stevenson were the others to come into the team.
Teenage academy players Mitch Aston, Koby Mottoh and Sam Folarin were all named among the substitutes.
Both sides showed plenty of attacking intent in the opening stages, although there was not much for either keeper to deal with.
But Pompey’s job was made a lot harder when they were reduced to 10 men with just 19 minutes on the clock.
Theo Archibald collected Aaron Dinan’s pass and was brought down by Raggett right on the edge of the box, with referee Stephen Parkinson brandishing a red card.
It might have got even worse for the visitors from the resulting free-kick, but Schofield managed to deal with George Moncur’s strike.
The keeper then did well to get down to his right and use his fingertips to divert a drilled Drinan effort around the post.
Pompey were not just going to sit back and soak up pressure, though, and were causing Orient plenty of problems.
They almost took the lead after Whyte took a magnificent touch to beat Ed Turns and then cut the ball back for Jewitt-White.
But Saydee nipped in to claim the shot for himself and, much to his team-mate’s frustration, could only fire wide.
The Blues did take the lead just before the break, however, from a move that started with another piece of neat Whyte footwork.
Jewitt-White then received the ball wide on the right and his low cross was laid off by Yengi for SAYDEE to take a touch and roll a shot into the bottom corner.
There was still another chance for the hosts before the whistle blew, but Schofield beat away Archibald’s attempt.
Half Time: Leyton Orient 0 Pompey 1
The hosts made a double switch at the break, with former Fratton loanee Pigott one of those to come on.
And they immediately had two great chances to level the contest, with a deft flick from Ruel Sotiriou hitting the post.
A Tom James free-kick was then met by Pigott, although his close-range effort was kept out by an alert Schofield.
But Pigott did level with a neat swivel and finish after being found inside the box by Jayden Sweeney.
Mousinho freshened things up with a switch just past the hour mark, as Whyte made way for Terry Devlin.
The visitors were still looking to get forward themselves and Saydee had a shot blocked after Swanson’s corner was cleared into his path.
Another change followed on 73 minutes, with Jewitt-White given a warm reception as he made his way off for Conor Shaughnessy.
And Pompey restored their lead moments later after Stevenson had intercepted the ball in the middle of the pitch.
He found Yengi, who in turn laid a pass off for KAMARA to race onto, surge into the box and slot home a neat finish.
But the Blues were indebted to their keeper for remaining in front, with Schofield doing brilliantly to deny Drinan from point-blank range.
There were more substitutions on 85 minutes, with Joe Rafferty and debutant Folarin on for goalscorers Kamara and Saydee.
And Pompey did well to see out the closing stages amidst little fuss to comfortably secure safe passage.
Leyton Orient (4-2-3-1): Howes; James, Beckles, Turns (Galbraith 46), Sweeney; Pratley (c), Brown (Happe 69); Archibald (Pigott 46), Moncur, Sotiriou (Pegrum 69); Drinan
Goals: Pigott 58
Subs not used: Brynn, Welch, Mohamud
Pompey (4-2-3-1): Schofield; Swanson, Raggett (c), Towler, Hume; Jewitt-White (Shaughnessy 73), Stevenson; Kamara (Rafferty 85), Saydee (Folarin 85), Whyte (Devlin 64); Yengi
Goals: Saydee 44, Kamara 74
Sent off: Raggett
Subs not used: Norris, Aston, Mottoh
Referee: Stephen Parkinson
Attendance: 2,371 (1,065 Pompey fans)