The match appeared to be heading for a 1-1 draw as it entered extra-time, after Joe Morrell had cancelled out Rafa Ramos’ opener for the hosts.
However, in stoppage time, Harry Jewitt-White headed home from close range and then Destiny Ojo raced clear to make it 3-1 moments later in front of a 2,250 Privett Park crowd.
John Mousinho used 21 players, with only Will Norris completing the full 90 minutes, as he made nine substitutions of 64 minutes.
The late finale flattered Pompey, but here are our player ratings...
5. Connor Ogilvie - 7
(Replaced by Jack Sparkes on 46 mins) Little was asked defensively, so largely occupied his time charging down the left flank and willing to back up Pompey attacks. A gentle introduction to friendlies, which was ideal. Photo: Jason Brown
6. Marlon Pack - 8
(Replaced by Tom Lowery on 46 mins) Looked like he had never been away for the summer. Drove Pompey’s game, spread the ball around and dictated their play and tempo. A couple of cracking tackles too. Photo: Gary Oakley
7. Ben Stevenson - 7
(Replaced by Owen Moxon on 46 mins) His first outing since injury in January and, as ever, looked composed and played with the minimum of fuss. Kept things ticking over with sensible use of the ball. Photo: Jason Brown
8. Anthony Scully - 6
(Replaced by Paddy Lane on 46 mins) Buzzed around and tried to make things happen, but nothing quite came off for the fit-again winger. Still, after last season's injury problems it was a welcome return to involvement - and there's still more to come. Photo: Jason Brown