Pompey’s play-off dream appeared to be fading fast.
But the Blues have injected new life into their bid for the top six with back-to-back victories closing the gap to just two points.
A three-point haul at snowy Oldham was followed by a first Fratton victory of 2018, as Oxford were vanquished in front of the Sky Sports cameras.
Kal Naismith grabbed an early opener before Alex Mowatt suffered a nightmare few seconds – missing a penalty and getting sent off in quick succession.
Brett Pitman made sure the numerical advantage counted with a brace and hopes Pompey can build more momentum over Easter.
The Blues skipper said: “We’ve had a tough time at home, so we’re delighted to come away with all three points.
"There’s a chance for us – we’ve given ourselves that with the results we’ve picked up in the last couple of games."
“Until Oxford went down to 10 men and we managed to get the second goal, they were probably on top. But we stuck in there and defended well.
"There’s a chance for us – we’ve given ourselves that with the results we’ve picked up in the last couple of games.
“We’ve got two coming up in the space of three days next week, so we’ll just take each one as it comes.”
Both of the striker’s goals were assisted by Jamal Lowe, who fancied a shot himself for the second before eventually deciding to pass.
Pitman said: “He should have just squared it to me in the first place after going around the goalkeeper!
“But credit to Jamal for getting the balls in there and we’re just really pleased overall to get the victory.”