A third successive loss in front of their own fans came against leaders Sheffield United on Tuesday.
"I keep saying that we've got eight games we need to win minimum," Appleton told BBC Radio Oxford. "But, the games are running out."
Oxford slipped to 11th and are nine points off the top six.
Twelve league games remain for the U's, who also have a trip to Wembley in the EFL Trophy final against Coventry City on 2 April.
"We are where we are for a reason," said Appleton as he reflected on his side's recent dip in home form.
"We're three or four players short of being able to compete with the that type of side (Sheffield United) most weeks in this division.
"The lads will pick themselves up and from an energy point of view, I can't ask any more from them."
Oxford United manager Michael Appleton insists his side are still in with a chance of reaching the League One play-offs despite another home defeat.