Neil Warnock has claimed even his West Ham counterpart Manuel Pellegrini could not understand how Cardiff City lost out at West Ham.
Joe Ralls missed a first-half penalty at London Stadium, with West Ham taking full advantage with three goals in a 12-minute burst after the break.
Lucas Perez, on for the injured Marko Arnautovic, scored twice and Michail Antonio added a third as West Ham seized control of the game, ensuring Josh Murphy's stoppage-time header was a mere consolation.
But Warnock revealed his bemusement as to how Cardiff slumped to a fifth-successive away defeat, meaning they remain two points above the relegation places.
"I don't know how we lost the game, let alone lost it 3-1," Warnock, whose side face fellow strugglers Southampton next time out, told BBC Sport.
"I called Manuel over and said, 'how are we losing 3-0?'. He said: 'I don't know'.
"The defending for the goals we have conceded this season has been appalling and we need to work hard on the training ground to eliminate these things.
"You can't fault them, we have won three games from behind, it shows the character, we have just got to stop making silly mistakes. Three mistakes for goals and that's cost us."
Arnautovic's barge on Junior Hoilett gifted Cardiff the chance to take the lead from the spot midway through the first half, yet Ralls – who seemed to overrule Victor Camarasa when it came to deciding who would take the penalty – fired a tame effort that was easily saved by goalkeeper Lukasz Fabianski.
And Warnock acknowledged that the midfielder is not likely to be on penalty duties next time around.
"You have got to put penalties away. The crowd were just about to turn and then we make it easy for them with three goals in 12 minutes and they don't have to worry about a system or anything," he added.
"Joe was last year's penalty taker so Camarasa will take the next one."
Pellegrini, meanwhile, praised the impact of substitute Perez, who grabbed a five-minute double to end a scoreless run in the Premier League that stretched back to January 2017.
2 - Lucas Perez is the first West Ham player to score twice from the bench in a Premier League game since Paulo Wanchope vs Newcastle in April 2000. Memories. December 4, 2018
"It was a strange game. We had chances but didn't score," Pellegrini told reporters. "Cardiff had some shots and then they got a penalty which was very unnecessary, fortunately Lukasz saved it.
"Perez is very important for the team, his goals. After that, for different reasons, Lucas didn't start so often but it is important that when the player has the chance, he takes it."
