Bristol City manager Nigel Pearson said:
"We didn't move the ball quickly enough and couldn't find enough moments of quality.
"It was clear Cardiff were prepared to let us have the ball… it was a bit of a careless performance from us in some ways.
"But the players have been brilliant over a sustained period… it's a frustrating end to the week.
"It was one of those days. I haven't been critical of us in recent weeks. We lost the game today because we didn't defend with the urgency we have shown recently."