Eden Hazard returned to the starting line-up after being rested for Chelsea's Europa League victory in Greece on Thursday
Chelsea's 100% start to the Premier League season came to an end at West Ham because Eden Hazard was not allowed to influence the game, says Hammers manager Manuel Pellegrini.
Blues boss Maurizio Sarri started his Stamford Bridge reign with five straight league wins but his team could not extend that record and had to settle for a goalless draw against battling opponents on Sunday.
Pellegrini - whose side had lost their previous two home league matches - was pleased with how West Ham "allowed Chelsea to have possession" on the right side of the pitch, denying the "dangerous" Marcos Alonso and Hazard much ball on the left.
"We played well tactically because we allowed them to have the ball where we wanted, and we defended well," said Pellegrini.
"They played most of the game on their right side, so they didn't create too many chances."
In the end, Chelsea were grateful for Andriy Yarmokenko's glaring second-half miss, when he headed wide with only keeper Kepa Arrizabalaga to beat and the goal at his mercy, for not suffering their first defeat.
The visitors had chances of their own, with West Ham keeper Lukasz Fabianski saving well from substitutes Alvaro Morata and Ross Barkley - but in the end a draw was a fair result in a game that rarely sparked into life.
It is a result that drops Chelsea into third place behind Manchester City on goal difference and leaves Liverpool two points clear at the top of the table with a maximum return from their six games.
Chelsea missing the magic touch
Lukasz Fabianki denied Alvaro Morata from close range
Hazard has been in magnificent form for Chelsea this season, exemplified by the superb hat-trick that inspired victory after they fell behind to Cardiff City at Stamford Bridge.
On Sunday, the brilliant Belgian was kept in check by West Ham and consequently the Blues' threat was hugely reduced, with winger Pedro injured and striker Olivier Giroud on the periphery.
Chelsea's best chance fell to the feet of substitute Morata after he replaced Giroud in the 65th minute, but he was thwarted by the bravery of Fabianski.
It summed up the visitors' frustration as their 100% winning start came to an end in a performance that was flat and lacking in energy, perhaps understandable after Thursday's trip to Greece to face PAOK in the Europa League.
Ross Barkley almost snatched it late on with a long-range effort that brought another excellent save low to his left from Fabianski, but this was not a Chelsea display that deserved three points.
The Blues remain undefeated under Sarri in competitive action and, despite the dropped points here, this still represents a satisfactory start for the Italian.
West Ham rue Yarmolenko miss
Andriy Yarmolenko had the best chance to score with just over 10 minutes remaining at London Stadium
Yarmolenko was voted man of the match by those who make the decision on behalf of West Ham - but in reality he was the villain of the piece despite another performance of promise.
The 28-year-old Ukrainian showed his class with two goals on his full debut in the 3-1 win at Everton, and almost delivered a trademark finish on Sunday when he cut inside and shot narrowly over with his left foot, his stock in trade.
Sadly for Yarmolenko and the Hammers, he missed his golden opportunity when it came at London Stadium - as substitute Robert Snodgrass landed a perfect cross on his head just six yards out at the far post in the second half.
However, with Chelsea keeper Kepa totally exposed, Yarmolenko somehow directed his header wide when it was easier to score.
It was West Ham's last chance of a performance not short on endeavour but missing inspiration in attack without the talent and unpredictability of Marko Arnautovic.
Declan Rice's display was once again a major plus, the 19-year-old showing composure in a defensive midfield role as he adds another string to his bow after showing his talent as a central defender.
West Ham's fans greeted the final whistle and a point at home warmly - but the dejected Yarmolenko and manager Pellegrini will know it could have been three.
Blues gear up for key week
Chelsea now face Liverpool twice in a week when we may get a more accurate measure of how far they have come under Sarri - and how far they still have to go after he succeeded Antonio Conte.
The Carabao Cup meeting at Anfield on Wednesday (19:45 BST kick-off) will merely be a warm-up - because both Sarri and his Liverpool counterpart Jurgen Klopp are sure to play shadow teams.
Stamford Bridge will host the acid test in the Premier League at 17:30 on Saturday, with the Reds flying high after winning their first six league games for the first time in 28 years and Chelsea attempting to claw back the ground they lost here at London Stadium.
It is hardly a defining few days for either team with the season in its infancy - but it is certainly the opportunity to strike a psychological blow.
-- Courtesy of BBC Sport