Kevin Ball felt several of his players didn't produce the effort required as the under-21s suffered a 4-0 home defeat at the hands of Aston Villa yesterday.
A second-half hat-trick from Michael Drennan and a single Graham Burke strike saw the visitors head south with all three points in the Barclays U21 Premier League.
And Ball pulled no punches in his post-match assessment, saying some members of the team "let down" the side as a whole.
"Over the previous three games we'd been smashing and I can't take that away from the players," he said.
"But the biggest thing is continuing to put things into practice when you think you're doing well, otherwise it bites you on the backside, which happened badly.
"Individually, too many players didn't put in the effort required to give Villa a good game and help the team.
"You have to put a shift in for the team, and if you're not prepared to do that the team will suffer, and you as an individual more so."
He added: "We were always on the back foot. It could have been more than four goals.
"One or two of the players weren't honest with themselves. They've let themselves and their team-mates down very badly and I can't accept that."