Alan Pardew says he will have to make changes after his Crystal Palace side "defended so badly" in their 5-4 defeat to Swansea.
Palace went ahead at the Liberty Stadium through Wilfried Zaha and looked in control until Jason Puncheon gave away a free-kick which Gylfi Sigurdsson dispatched shortly before the break.
After falling 3-1 behind following two Leroy Fer goals, Palace fought back to go 4-3 ahead in the 84th minute when Christian Benteke scored, but two stoppage-time strikes from Fernando Llorente condemned Palace to their sixth straight league defeat.
Palace had come under criticism for their handling of set-pieces prior to Saturday's fixture and Pardew was left furious after further lapses in his backline, revealing he will take action following the result.
"For us it was a game that we defended so badly at times in set-plays, something we talked about and worked on and I feel aggrieved about that," said Pardew. "Particularly when we take the lead 4-3 there's no way we should concede those goals and I'll have to look to make changes there."
Swansea boss Bob Bradley described the manner of his side's victory as "extra special", but for Pardew the late defeat should never have happened.
When asked if the way in which his side lost made it worse, Pardew said: "It does. We scored the first goal, were in total control."
Connor Wickham was forced off on a stretcher shortly after the break with the scores level, and Pardew believes the potentially serious injury was a key moment in the game.
The Palace boss, whose position reportedly has come under pressure with the Eagles having not won in the league since September 24, also claimed Sigurdsson's free-kick wrongfully turned the tide in south Wales.
"I thought the referee gifted them that free-kick on the edge of the box where they got an equaliser," said Pardew. "The momentum shifted.
"The injury to Connor shifted the momentum once more. It's a bad injury for us. Then it went into a crazy period.
"Unfortunately we let ourselves down defensively. You cant score four goals away from home and not win. That is just not right.
"Four of their goals are from set-plays, we have got to be better than that. I'm going to have to make changes I think."
Pardew admitted the club will not know the extent of Wickham's injury until scans on Sunday, but remained coy when asked about where the defeat leaves his future as Palace boss.
"I'm a manager of a football club with six defeats at the moment," he said. "It's hurting."