Steve Stone bemoaned a ‘sub-standard’ performance as the Clarets let go of their grip on a play-off place.
A 3-2 defeat at Bristol City – only Burnley’s second loss in 12 games across all competitions – kept Stone’s men third in the Professional Development League’s northern section.
And the U23s’ boss admitted the players’ approach at Ashton Gate had not been right as they surrendered an early lead and missed a second-half penalty to give away the points.
“They dipped well below the standards I’ve tried to set them, but that they have set themselves,” said Stone.
“They are a good bunch who work hard and grind out results and don’t give goals away.
“We gave three away today which we haven’t done for quite some time, so that’s probably the most disappointing thing.
“All the things you look at to be a professional footballer, your endeavour, your work-rate to close people down to win the ball back, all the horrible things I always talk about, were missing today.
“And when that’s missing, that’s a worry for lads who are trying to come through.
“Sometimes you can lack quality, and lack quality in the final third, but if you’re trying to put a shift in and do your bit for the team you accept that sometimes, but that was unacceptable.
“We should go and win those sorts of games. They had scholars out and we had first-year pros and were made to look second-rate in the second half for 20-25 minutes and that’s down to work-rate and commitment in that period of the game.”
The Clarets failed to build on a superb long-range strike from Rob Harker after just two minutes as they let City off the hook.
After Jordan Cropper’s spot-kick miss early in the second half, the Robins struck twice in 16 minutes to lead 3-1.
And a last-minute Dan Agyei penalty was not enough to spark a dramatic late fight as the Clarets now trail Birmingham on goal difference with three games to go as they chase the runners-up spot behind Leeds United and a place in the title play-offs.
“In terms of the league position and wanting to get through to the play-offs, I told them they had to win,” added Stone, whose side faces Leeds in the PL Cup quarter-finals on Friday.
“It was our game in hand. The most disappointing thing for the boys’ point of view is that the league position is now under threat.”