THIS was a flat, off-colour performance from a Chelsea side that had being showing real promise under manager Frank Lampard.

Aaron Cresswell scored the only goal of this match as West Ham won this London derby. In so doing, they eased some of the pressure on under-fire boss Manuel Pellegrini.

Meanwhile, the Chelsea manager remains confident ahead of Wednesday’s match against Aston Villa.

“I still believe in the squad,” said Lampard, a former West Ham player. “There will be questions that will be asked but I do believe in the squad.

“This is not the time for harsh reactions or judgements. It’s time for a look at a bit of character to see how our reaction is for Aston Villa.”

It would have been very different had Chelsea’s players imposed themselves from the start of the match. However, it proved to be a frustrating first half for the home supporters.

Against a struggling West Ham, who came into the match without a win in nine matches, the home side should easily have taken control of their opponents.

Reece James’s deflected shot hit the woodwork on 23 minutes. It is the closest they got, and as the match wore on, the goal-scoring opportunities soon dried up.

Lampard had rested N’Golo Kante, Cesar Azpilicueta and Willian. In addition, Olivier Giroud was spearheading the attack for Chelsea in the injury-enforced absence of Tammy Abraham.

The Frenchman, who hadn’t started a match since August, showed his lack of match sharpness with a poor display.

West Ham’s goal came shortly after the interval, and after a period of pressure from the away side.

Cresswell, one of the better performers for the visitors, found space in the Chelsea penalty area. He cleverly cut in onto his right foot away from the defender before curling the ball low beyond the diving Chelsea goalkeeper Kepa Arrizabalaga.

Few could have blamed West Ham’s players for the euphoric celebrations at the final whistle. This was their first win at Stamford Bridge in 17 years.

West Ham’s players, including 33-year-old goalkeeper David Martin making his league debut for the club, reacted jubilantly to the win. At the final whistle, he passionately embraced his father, club legend Alvin Martin.

Pellegrini said: “Yes [I’m pleased], for the result and not conceding goals. The most difficult thing was not to be worried about the job or the future, it was to keep the players keeping the style.”

West Ham travel to Wolverhampton Wanderers looking to build upon the result.