Oxford boss Chris Wilder felt the dismissal of Damian Batt changed the game following his side's 2-1 defeat to Bradford.
The defender received his second yellow just before half-time for a foul on Kyel Reid. And second-half goals from acting skipper Craig Fagan and substitute striker James Hanson helped the Bantams to victory, despite Asa Hall pulling a goal back to set up a frantic finale.
Wilder said: "Bradford started better than us and deserved to be in the lead. The sending-off changed the balance of the game and Bradford capitalised on that and scored the second against the run of play.
"We then got one back and it was very open after that because we wanted to get something out of the game. We played an attacking formation because we wanted to win it, but this was always going to be a difficult fixture because Bradford are a good side.
"The first 25 minutes or half an hour was the best we have had to deal with for a long time. Bradford got quickly out of the traps and it was a a heavy bombardment we had to take.
"I think we've got the chance of going up automatically - we've got the ability. We have only lost two matches in 15 and there is lots to play for and nothing to be disappointed about. We've just got to make sure we get back to winning ways."