Neil Harris questioned his Cardiff players' desire and challenged them to regain a winning mentality following a 2-1 loss at struggling Wycombe.
Ryan Tafazolli and David Wheeler steered the Chairboys to a rare Sky Bet Championship win, with Junior Hoilett's stoppage-time goal just a consolation.
Defeat on the road clearly irked Harris, sent off for dissent late on, whose side have lost three consecutive games for the first time in his tenure.
"We're conceding too many goals, we haven't got a clean-sheet mentality and we're too soft," he said.
"We're too far from the top six for my liking.
"Losing games like tonight in the manner we did is disappointing, it's not good enough for me.
"Conceding goals like this is just not acceptable. Where's the winning mentality? Where's the clean-sheet mentality? We had it for so long and it's disappeared.
"It just can't happen if you want to compete at the top end of this league. I don't see us doing the hard yards to stop crosses.
"I don't see us putting a head in where it hurts. Is there enough leadership, is there enough desire to want to do well?"
Harris also said that the upcoming transfer window will be unlike any other and suggested the financial worries of Championship clubs are deeper than what has been reported.
He added: "We're not going to go and spend money in January, no one is, it's just not possible.
"Clubs, not us, are struggling to pay wages, there's loads not being reported about clubs in the Championship not paying wages, it's going under the radar.
"So going and signing lots of players on lots of money is not going to happen.
"We're going to try and adjust the group, yes, but to bring players in, players will have to go out."
This win was vital for manager Gareth Ainsworth and Wycombe, who took the lead when Tafazolli powered in from a corner.
Wheeler wrapped up the points in the second half, rounding off a sweeping move from close range, sealing Wycombe's third Championship win and their first since November 4.
"It feels amazing," said Ainsworth. "It's been coming, I can't say it hasn't. We've been performing so well and people will have been screaming at the TVs thinking results is the game, not performances.
"I wanted a win, I said maybe we would play badly and get the win, but we played well and I'm really proud of the boys, they gave me everything.
"As a manager, that's all you want. Back-to-back wins would really propel us up the table.
"There's teams now that have been above the line that are going to fall below it – what's that going to do to them mentally?
"We've been below it all year and we're going to get above it at some stage, and I can't wait for that.
"The ones who drop down under it, that's important for their mental side. I still believe we're going to survive in this league."
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