Substitute Jefferson Louis won the game for Oxford United at the Kassam Stadium with his first League goal.
It was enough to lift them back into the promotion play-off zone and dump Swansea City to the bottom of Nationwide Division Three.
The goal was set up by Chris Hackett - a 58th minute substitute for Manny Omoyimni who limped off with a pulled hamstring.
Five minutes later he raced between two defenders and Louis was in position to drive in the low cross.
Louis' other goal for Oxford was the winner against Charlton Athletic in a penalty shoot-out in the Worthington Cup.
Oxford had a setback when striker Gavin Gordon pulled a hamstring and was replaced by David Oldfield after 17 minutes.
His departure left them desperately short of firepower and a shot by Omoyimni on the stroke of half time was their only threat. However, the course of the game changed with the arrival of Hackett.
It was Oxford's best win at the Kassam Stadium since the 2-1 success over Bury on the opening day of the season and was largely due to a brilliant double save by keeper Andy Woodman in the seventh minute.
He somehow managed to divert a firm drive by John Keaveney on to a post and leapt spectacularly to his right to keep out Steve Watkin's follow-up attempt.
The win delighted Oxford manager Ian Atkins.
"We earned the right to that win because of our doggedness in the first half," he said.
"We had four strikers out before the start and another two injured during the game so it made things very difficult for us.
"Tell me another club that's lost six strikers and still wins a game," he added.
Swansea boss Brian Flynn bemoaned Woodman's brilliant saves early in the game. "Goals change games and if we'd scored then it might have been very different," he said