Christian Saydee came off the bench to grab a precious winning goal for Pompey against Oxford at Fratton Park.
That came after Callum Lang’s early opener was almost immediately cancelled out by a Cameron Brannagan penalty.
Both sides played their part in an absorbing contest that contained plenty of chances, but it was the Blues who held on to claim a valuable victory in the race for promotion.
John Mousinho made one change from the side that were held to a draw at Charlton the previous week.
Myles Peart-Harris was restored to the starting line-up, occupying a deeper role than usual in place of Owen Moxon.
There was a familiar face in the opposition team, with former Blues loanee Owen Dale included – having already scored at Fratton Park for Blackpool earlier in the campaign.
The ground was rocking from the off and only got louder when the hosts broke the deadlock with just 88 seconds on the clock.
A quick Joe Rafferty throw was chested by Colby Bishop into the path of Abu Kamara, who then laid the ball off for LANG.
The January signing took a nice first touch to beat Elliott Moore and then hit a shot that Jamie Cumming could only fumble into the net.
It might have got even better when Marlon Pack swung a free-kick into the mixer, but Conor Shaughnessy could not keep his header down.
Pompey were not ahead for long, however, and when Mark Harris found Dale in the box, he was brought down by Sean Raggett.
Referee Ben Toner pointed straight to the spot and Brannagan stepped up calmly slot home the penalty.
The chances kept coming at both ends of the pitch and when Bishop collected Pack’s threaded pass, his shot was prevented from finding the top corner by a fine Cumming save.
There was soon a switch in action, with Harris curling a shot against the post before Fin Stevens’ effort was punched away by Will Norris.
A low Kamara drive was saved by Cumming, with the contest starting to resemble a basketball game as it switched from one side to the other.
The home team, meanwhile, were growing increasingly frustrated by a series of soft free-kicks being awarded against them by Toner.
One of which came when Lang was clearly being fouled himself right in front of the assistant referee, with the Pompey forward booked for dissent.
There was one more chance just before the break, when a Peart-Harris drive was crudely ended by Rúben Rodrigues right on the edge of the box.
Paddy Lane laid the free-kick off for Pack, whose low effort flew under the wall, but also into the arms of Cumming.
Half Time: Pompey 1 Oxford 1
It was the visitors who were first to threaten following the restart after Josh Murphy’s initial effort was blocked by Rafferty.
The ball landed straight back at the feet of the United winger, who lashed a fierce shot against the crossbar.
Pompey soon had an opening of their own after Bishop and Lang combined to find Lane, only for Moore to make a superb challenge inside the box just as he shaped to shoot.
Mousinho freshened things up with a change just past the hour mark, as Lang – on a yellow card – made way for Saydee.
It was soon Oxford’s turn to threaten again, with Shaughnessy and Rafferty making key blocks in quick succession to keep them at bay.
Pompey were left cursing Toner once more when a soft free-kick was awarded against the home side – although the referee was soon being hailed.
He played an advantage after Bishop was fouled in the middle of the pitch, allowing Pack to launch a fine pass forward.
SAYDEE raced onto it and rode the challenge of Ciaron Brown before calmly tucking away his first league goal for the club.
Oxford were still looking dangerous, though, and soon had a series of chances one after the other, starting with a Murphy effort that was finely saved by Norris.
Dale’s strike was then blocked by Shaughnessy, while from the resulting corner, Saydee did brilliantly to turn Brown’s header over.
There was another change for Pompey on 79 minutes, as Peart-Harris made way for Moxon in the middle of the park.
And another two followed in the closing stages, with Josh Martin and Kusini Yengi replacing Kamara and Bishop.
Oxford were showing plenty of urgency as the seconds ticked down, but backed by a raucous home support, the Blues held on for the win.
Pompey (4-2-3-1): Norris; Rafferty, Raggett, Shaughnessy Ogilvie; Pack (c), Peart-Harris (Moxon 79); Kamara (Martin 88), Lang (Saydee 64), Lane; Bishop (Yengi 88)
Goals: Lang 2, Saydee 67
Booked: Lang, Ogilvie, Kamara, Bishop
Subs not used: Macey, Towler, Sparkes
Oxford (4-2-3-1): Cumming; Stevens, Moore (c), Brown, Leigh; McGuane (Henry 83), Brannagan; Dale, Rodrigues (Bodin 75), Murphy; Harris (Goodwin 75)
Goals: Brannagan 6 (pen)
Booked: Harris, Rodrigues, Henry
Subs not used: Eastwood, Bennett, Thorniley, Matete
Referee: Ben Toner
Attendance: 20,303 (1,382 away fans)
