QPR boss Marti Cifuentes bemoaned his team's "unacceptable" defending from set-pieces after their 2-1 defeat at home to Cardiff.
Struggling Rangers have consistently conceded from set-pieces this season and did so twice more against the Bluebirds.
Paul Smyth equalised for the hosts to cancel out Dimitrios Goutas' opener, but Rangers' defensive shortcomings were badly exposed again as Perry Ng scored the winner.
Cifuentes, who took over at the end of October, said: "We knew that they were a good team from set-pieces and then they score from that situation.
"We got good momentum in the second half and scored a goal. Then we lost this momentum. We conceded another goal from a set-piece, which is unacceptable.
"I've been in charge for 12 games and we've conceded 11 goals, which is quite a decent defensive performance. But seven of them have been from set-pieces, which is unacceptable.
"That area of the game should be an asset, not a liability, and we are getting extremely punished.
"If we concede two goals from set-pieces then we cannot expect to win matches."
Rangers are third from bottom, have gone five matches without a win and badly needed three points from the first of four crucial home league matches this month.
They picked up a useful point in a 0-0 draw at Ipswich on Friday, but playmakers Ilias Chair and Chris Willock both went off injured in that game and were badly missed against the Bluebirds.
"It was definitely very far from the result and performance we wanted," admitted Cifuentes, ahead of their FA Cup third-round tie with Bournemouth at Loftus Road on Saturday.
"It was an opportunity to kick off the year with a positive result for our fans, to change the energy a little bit and to keep building after a good point against Ipswich.
"Unfortunately, we were not good enough. The first half is really disappointing - really poor. It's not that Cardiff created chances."
Cardiff boss Erol Bulut praised his players and is hoping to add to his squad during this month's transfer window.
He said: "From tomorrow, we're going to start to have some meetings so we can make some quick movements with the transfers.
"So let's see. I hope that in the weeks of January we will finalise what we need.
"We'll discuss what we can do - what is the best way for Cardiff City and the team."
Bulut's side defended well at Loftus Road and took their chances when they came.
"It was perfect to have a win for the new year. It was not the greatest game, but the way we won it was great," said the Turkish manager.
"We have injuries and illness so I have limited possibilities, so I can say it was a great game for us.
"The team showed fighting spirit - winning spirit. Some games are like that and today it was like that.
"Of course, for the offensive part, we want to create more and finalise more, but we have to compliment our defenders. Sometimes you have to count on your defenders and they are doing well."
*copy from PA.
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