Kit Symons says that Fulham's poor defending cost them during their 3-2 loss to Sheffield Wednesday on Saturday.
The Lilywhites conceded from three set pieces, with Ross Wallace setting up all three goals for the Owls.
"Poor defending from set-pieces and balls into our box cost us very dearly. That side of our game wasn't good enough," Symons told BBC Sport.
"Take them out of it and we played pretty well, so I'm torn between two stools. I'm annoyed with the defending from set-pieces and balls played into the box but I'm proud of the way the players performed, especially in the second half.
"We'll always score goals and we need to start getting a couple of clean sheets now."
Fulham are sitting in 16th in the Championship table after Saturday's results.
