Oxford boss Chris Wilder bemoaned his side's lack of cutting edge after their 2-0 defeat to Hereford.
Stuart Fleetwood netted in the eighth minute and sealed the points for the Bulls at the death to extend their unbeaten run to five league games.
Wilder said: "I can't batter my team in the dressing room. It was a decent performance.
"From tee to green we've done really well, but as always it's about the two main parts of the pitch - in both boxes.
"We switched off and they scored, and we didn't take our chances."