Former Chelsea player Emerson Palmieri scored against his former club to earn West Ham a point and increase the pressure on Blues boss Graham Potter.
Chelsea fielded a new-look £200m forward line but, despite taking the lead, were once again frustrated and have won just once in seven Premier League matches.
Joao Felix had already had a goal ruled out for offside when the Portugal forward fired visitors Chelsea ahead with a volleyed finish following a delicious assist by Enzo Fernandez, the £107m British transfer-record signing from Benfica.
Kai Havertz thought he had doubled the lead only for Chelsea’s celebrations to be cut short by another offside flag, before West Ham equalised through Italy international Emerson’s first Premier League goal.
The 28-year-old, who spent four years at Stamford Bridge, finished at the far post after Vladimir Coufal’s cross was flicked on by Jarrod Bowen.
Chelsea, who have dropped 14 points in the last seven top-flight matches, carved out the better chances but could not make them count.
Noni Madueke was lively on his first start for the club since his £30.7m arrival from PSV Eindhoven and the 20-year-old forced a fine save from Lukasz Fabianski before the West Ham keeper kept out a free-kick by Felix.
In a dramatic finish, West Ham thought they had won it in the closing stages when substitute Tomas Soucek scored from close range but it was ruled out for offside – the third disallowed goal of the match.
This was another hugely frustrating day for Potter and Chelsea as strong appeals for an 89th-minute penalty were waved away after Soucek appeared to handle Conor Gallagher’s shot inside his own box.
Chelsea continue to stutter under Potter
Chelsea, who have already been eliminated from both the FA Cup and Carabao Cup, resume their Champions League campaign against Borussia Dortmund on Wednesday on the back of a poor run of form.
They have taken just seven points out of the last 21 on offer and are well adrift in the race to finish in the top four, despite their heavy spending over the past two transfer windows.
In addition, they are without an away win in the league since October, a run of seven matches which included losses at Potter’s former club Brighton & Hove Albion, Newcastle United and Fulham.
Chelsea had seven players under the age of 24 in their starting line-up, including Madueke, Felix, Mudryk and Havertz.
There were encouraging signs as the young forward line caused problems in the first half but Chelsea were disappointing in the second half and have now scored just 23 goals in 22 league games.
They continue to stutter under Potter, who has won just five of his 16 top-flight matches since taking charge in September.
More to follow.
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West Ham United
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Squad number1Player nameFabianski
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Squad number24Player nameKehrer
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Squad number21Player nameOgbonna
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Squad number27Player nameAguerd
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Squad number5Player nameCoufal
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Squad number11Player nameLucas Paquetá
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Squad number41Player nameRice
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Squad number33Player nameEmerson
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Squad number20Player nameBowen
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Squad number22Player nameBenrahma
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Squad number9Player nameAntonio
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Squad number2Player nameJohnson
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Squad number12Player nameDownes
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Squad number18Player nameIngs
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Squad number28Player nameSoucek
Chelsea
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Squad number1Player nameArrizabalaga
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Squad number24Player nameJames
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Squad number6Player nameThiago Silva
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Squad number4Player nameBadiashile
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Squad number32Player nameCucurella
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Squad number12Player nameLoftus-Cheek
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Squad number5Player nameFernández
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Squad number31Player nameMadueke
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Squad number11Player nameJoão Félix
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Squad number15Player nameMudryk
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Squad number29Player nameHavertz
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Squad number19Player nameMount
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Squad number21Player nameChilwell
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Squad number22Player nameZiyech
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Squad number23Player nameGallagher
Line-ups
West Ham
Formation 3-4-2-1
- 1Fabianski
- 24Kehrer
- 21Ogbonna
- 27AguerdSubstituted forJohnsonat 80′minutes
- 5CoufalBooked at 55mins
- 11Lucas PaquetáSubstituted forSoucekat 14′minutes
- 41Rice
- 33Emerson
- 20Bowen
- 22BenrahmaSubstituted forDownesat 67′minutes
- 9AntonioSubstituted forIngsat 67′minutes
Substitutes
- 2Johnson
- 8Fornals
- 10Lanzini
- 12Downes
- 18Ings
- 28Soucek
- 47Hegyi
- 49Anang
Chelsea
Formation 4-2-3-1
- 1Arrizabalaga
- 24James
- 6Thiago Silva
- 4BadiashileBooked at 64mins
- 32CucurellaSubstituted forChilwellat 67′minutes
- 12Loftus-CheekSubstituted forGallagherat 79′minutes
- 5Fernández
- 31MaduekeSubstituted forMountat 68′minutes
- 11João Félix
- 15MudrykSubstituted forZiyechat 67′minutes
- 29Havertz
Substitutes
- 13Bettinelli
- 14Chalobah
- 19Mount
- 21Chilwell
- 22Ziyech
- 23Gallagher
- 27Fofana
- 28Azpilicueta
- 30Chukwuemeka
Live Text
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Match ends, West Ham United 1, Chelsea 1.
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Second Half ends, West Ham United 1, Chelsea 1.
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Ben Chilwell (Chelsea) wins a free kick in the defensive half.
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Foul by Jarrod Bowen (West Ham United).
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Foul by Ben Chilwell (Chelsea).
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Jarrod Bowen (West Ham United) wins a free kick on the right wing.
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Corner, West Ham United. Conceded by Ben Chilwell.
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Attempt blocked. Conor Gallagher (Chelsea) left footed shot from outside the box is blocked. Assisted by Kai Havertz.
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Foul by Reece James (Chelsea).
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Flynn Downes (West Ham United) wins a free kick in the defensive half.
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Delay over. They are ready to continue.
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VAR Decision: No Goal West Ham United 1-1 Chelsea.
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GOAL OVERTURNED BY VAR: Tomás Soucek (West Ham United) scores but the goal is ruled out after a VAR review.
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Offside, West Ham United. Emerson tries a through ball, but Declan Rice is caught offside.
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Foul by Hakim Ziyech (Chelsea).
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Danny Ings (West Ham United) wins a free kick on the left wing.
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Substitution, West Ham United. Ben Johnson replaces Nayef Aguerd because of an injury.
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Delay over. They are ready to continue.
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Delay in match because of an injury Nayef Aguerd (West Ham United).
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Substitution, Chelsea. Conor Gallagher replaces Ruben Loftus-Cheek.
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