Chris Wilder admitted he was disappointed with Tom Craddock's reaction at his substitution in Oxford's 1-0 loss at home to Wycombe.
Joel Grant's magical strike won the game for the visitors but Craddock missed the best chance to get the U's a point, heading Jon-Paul Pittman's cross over the bar from four yards before slicing wide another very presentable opportunity.
Craddock showed his displeasure at being subbed early in the second half by walking straight down the tunnel without acknowledging his replacement or anyone else.
"I was disappointed he missed two chances in the first half but I didn't rant and rave about it," he said.
"His reaction when he came off was disappointing but my assistant Mickey Lewis went after him and we've had a few words in the dressing room.
"Tom's one of those who's not going through a great time at the moment here, but he's a good character. It's a tough period when players are playing with no belief.
"I thought there was enough effort and commitment from the team, but it's a confidence issue.
"These are times that players have to go through, and managers have to go through. I'm desperate to come through it and improve the football club.
"A couple of them are really struggling to play at home, and they've got to be brave when they go out there on the pitch. It's understandable with the results we've had, that some find that difficult."
Oxford have now managed just one point from a possible 15 and their season is petering out painfully.