Pompey collected two points from a thrilling opening EFL Trophy group stage fixture against Fulham U21s at Fratton Park
It finished 3-3 after 90 minutes, but the Blues won a penalty shoot-out 5-4 to claim the additional spoils.
They fought back from falling behind to Chris Donnell’s close-range finish in the opening minute, as Sean Raggett and Terry Devlin turned the contest around.
But Martial Godo levelled for the visitors, who had George Okkas sent off for a second bookable offence just before the break.
A superb strike from Raggett restored the lead in the second half, but the Cottagers hit back through Delano McCoy-Splatt and the Blues missed a host of chances to wrap up the win.
It meant that penalties would be needed to gain an extra point and both sides missed one of the initial five before Ryan Schofield made the decisive save in sudden death.
John Mousinho changed his entire starting line-up from the League One draw with Cheltenham at the weekend.
Koby Mottoh came in for his full debut at the age of just 16, with Paddy Lane on the opposite flank and Abu Kamara slotting in just behind Christian Saydee.
Ben Stevenson and Devlin filled the midfield berths, while there were places for Jack Sparkes and Zak Swanson at full-back.
The defence was completed by Ryley Towler and stand-in skipper Raggett, stationed in front of home debutant Schofield.
Pompey got off to the worst possible start and found themselves trailing with just 56 seconds on the clock.
McCoy-Splatt sent the ball in from the right and Oliver Sanderson turned it towards goal, with Donnell making sure that it would cross the line.
But the Blues soon settled and Saydee played a quick free-kick to Lane, whose drilled effort was well saved by Alex Borto.
And they were level on 17 minutes, as Sparkes swung a dangerous corner into the box, with RAGGETT sliding in at the far post to score.
Mottoh was seeing plenty of the ball wide on the left, but after finding space to burst forward, his effort lacked the power to trouble Borto.
The hosts were soon ahead, however, as another fine cross, this time from Swanson, was met by a firm DEVLIN header to convert it.
Pompey were looking to put their foot down, but Boro raced from his box to beat Lane to the ball before the Northern Ireland international was unable to find the target from an acute angle.
And the visitors were handed an equaliser on 39 minutes, with Schofield not dealing with Stevenson’s back-pass and Godo sliding in to bundle the ball over the line.
The Blues looked for another response and Kamara volleyed narrowly over after being picked out by Lane.
Their opponents were then reduced to 10 men just before the break when Okkas received a second booking of the night.
Earlier penalised for a clumsy challenge on Lane, he prevented Pompey taking a quick throw and was shown a red card by referee Carl Brook.
Half Time: Pompey 2 Fulham U21 2
The hosts immediately got on the front foot when the action restarted and tried to make the most of their numerical advantage.
But it would have been very hard to predict just how they did manage to retake the lead on 51 minutes.
There was a cry of ‘shoooot’ from the Fratton faithful when RAGGETT received the ball from Towler and he obliged, sending a 35-yard rocket into the top corner.
The advantage was almost strengthened when Swanson’s centre was parried out by Borto, but the follow-up shot from Saydee was deflected behind.
Schofield then had to show quick reactions at the other end after a cross ricocheted towards the net off the chest of Sparkes.
It was breathless stuff and Pompey soon went close again, with a Saydee meeting Swanson’s corner and seeing his header rattle the crossbar.
The move was still alive, though, and when the ball fell for Raggett, he missed the chance to complete a hat-trick by firing over.
Mousinho freshened things up with a double switch just past the hour mark, as Anthony Scully and Alex Robertson replaced Saydee and Lane.
Pompey were proving wasteful in their attempts to wrap the points up and after taking a brilliant first touch, Robertson mis-cued his shot and Scully blazed the loose ball over.
Kamara then rose to get on the end of a teasing delivery from Sparkes, but could not keep his header down.
And they were made to pay for their profligacy on 73 minutes, when McCoy-Splatt swapped passes with Sanderson and slipped the ball past Schofield.
But the keeper then prevented the Cottagers going ahead, coming off his line to block a shot from Sanderson.
Pompey looked to get back in the ascendency and Borto soon came to Fulham’s rescue, first using his leg to deny Swanson and then keeping out Stevenson’s follow-up.
The keeper was soon at it again, this time diving his right to turn Robertson’s effort around the post after the midfielder had beaten a defender with some neat footwork.
And when Robertson did manage to beat Borto with a long-range drive on 88 minutes, the ball struck the base of the post.
After 90 Minutes: Pompey 3 Fulham U21 3
There were some excellent penalties in the shoot-out, with Raggett, Robertson, Scully and Kamara all finding the target with ease.
And although Swanson’s effort was well saved by Borto, Harvey Araujo immediately blazed over to keep the scores level.
Sparkes edged the Blues back into the lead and Schofield then flung himself to the left to keep out Devan Tanton’s effort and ensure the extra point remained at Fratton Park.
Pompey (4-2-3-1): Schofield; Swanson, Raggett (c), Towler, Sparkes; Devlin, Stevenson; Lane (Robertson 62), Kamara, Mottoh; Saydee (Scully 62)
Goals: Raggett 17, 51, Devlin 28
Booked: Stevenson, Robertson, Raggett
Subs not used: Smith, Quarm, Poole, Aston, Folarin
Fulham U21 (4-3-3): Borto; Tanton, Araujo, Esenga, Okkas; McCoy-Splatt (de Jesus 73), Dibley-Dias (c), Donnell; Works (Šekularac 83), Sanderson (McFarlane 90+1), Godo (Gofford 90+1)
Goals: Donnell 1, Godo 39, McCoy-Splatt 73
Sent off: Okkas (two yellow cards)
Booked: Tanton
Subs not used: McNally, Park, Gordon
Referee: Carl Brook
Attendance: 3,596 (109 away fans)