Lucas Perez scored twice to help West Ham blow away Cardiff 3-1 as Joe Ralls’ penalty miss proved costly on Tuesday.
Perez came in from the wilderness to score twice (49 & 54) after replacing Marko Arnautovic, who limped off with a hamstring problem. Michail Antonio added a third (61) before Josh Murphy (90+5) registered a late consolation for Cardiff.
It was former Arsenal striker Perez's first Premier League goals since January 2017 as West Ham made it back-to-back wins after turning over Newcastle on Saturday.
It could have been very different if Ralls had not spurned his chance from the spot just before the break at 0-0 but West Ham goalkeeper Lukas Fabianski guessed right.
Both teams started with a confident swagger after their respective wins at the weekend but it was West Ham who created the early opening.
Angelo Ogbonna had a close-range header turned over the bar by Neil Etheridge while Arnautovic had an effort cleared off the line after rampaging through the Cardiff backline.
The frustration of missing that chance may have affected Arnautovic's decision-making on 35 minutes when he barged over Junior Hoilett in the box. The West Ham striker was a relieved man when Ralls' weak penalty was easily saved by Fabianski.
Arnautovic's eventful evening came to end just before the break when he limped off with a hamstring injury.
His departure seemed to knock the Hammers, who looked short on ideas until Perez struck just after half-time. Robert Snodgrass produced a deft touch behind the Cardiff defence and the striker powered a finish past Etheridge, who could have done better.
Confidence was now flowing for Perez after a frustrating period of his career since moving to the Premier League - he doubled up six minutes later. This time it was Arthur Masuaku who opened up Cardiff and his pass was finished by the striker - once again, Etheridge will have been disappointed with his effort.
Antonio completed the scoring blitz six minutes later when flicking home a Snodgrass corner after Cardiff went to sleep from the set-piece.
Apart from a scrappy late Murphy goal, Cardiff had little in response. After an impressive win at Wolves, it's back down to earth for Neil Warnock's men.
Man of the match: Robert Snodgrass
For all the millions spent on foreign imports in the West Ham squad, it was the guile and creativity of Snodgrass that made the difference in this encounter. His delivery was first-class and he stepped up when West Ham needed him in a difficult period of the game where the crowd were becoming restless. His pass for Perez's opener was simple but beautifully constructed. He must be playing the best football of his career at the minute.
Manager reaction: Manuel Pellegrini
"We improved a lot in the second half. It was a relief. The goal relieved the pressure. That's why we scored two more goals. Cardiff are a difficult team - they only lost 1-0 against Tottenham and Everton. They work very well in the style they like to play."
Manager reaction: Neil Warnock
"Tonight showed we can win away games from home. I pulled Manuel Pellegrini in the technical area and said: 'how can we be losing 3-0' - it was a mad 12 minutes, then the penalty miss."
What's next?
West Ham are back at the London Stadium on Saturday for a home fixture with Crystal Palace while Cardiff face fellow strugglers Southampton.