Oxford manager Chris Wilder felt his side should have had a late penalty during the goalless draw against Gillingham.
Substitute Oli Johnson went down in the box following a challenge from Joe Martin but the referee booked Johnson for diving and the battle between two teams chasing a play-off place ended in stalemate.
"I don't see why the referee would think Oli would go down when he had a shot on goal. There was no reason for him to go down, it was a clear tug on him," said Wilder. "You need brave players in this game and you need brave referees. I'll look at the TV replays and if I'm wrong, I'll apologise to the ref, but that's how I saw it."
After a third successive home game without a win, the Us remain in seventh place only because Macclesfield came from behind to hold their play-off rivals Crewe to a draw.
Wilder added: "It was a hard-fought game and probably not the result that either team wanted. But who'd have thought that Crewe would only draw with Macclesfield?
"If we get into the play-offs with a goal in the last minute of our last game, at Port Vale, we'll take that."
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