Debutant Adrian Segecic was the hero, netting 38 minutes into his debut, having following up with a left-footed shot after Colby Bishop one-on-one was stopped.
The Australian, along with man-of-the-match Callum Lang, were absolute pests with their energy and drive throughout to stretch the home defence.
Pompey were challenged defensively late on – and always with Oxford’s long throws – but they stood firm to claim victory. And here are our playing ratings...
5. Conor Shaughnessy - 8
Great to see the old partnership with Poole reunited and the pair looked very solid together. A spell of sloppy passing in the first half, which was very uncharacteristic, but superb in the air, especially against the threat of Oxford’s long throws. Photo: Nigel Keene
6. Connor Ogilvie - 7
Appeared to be trying to get forward a lot more from left-back, yet understandably didn’t have the same connection with Bianchini as Murphy. Rock solid as ever. Photo: Steve Bailey
7. Andre Dozzell - 8
Operated further forward than Swift and knitted up the defence and the attack superbly. Has a handy knack of being in the right place at the right time. Photo: Steve Bailey
8. John Swift - 7
(Replaced by Zak Swanson on 86 mins) Played in the deep-lying central midfielder role and looked to dictate Pompey’s play, keeping things extremely simple. Encouraging debut. Photo: Paul Phelan