Chelsea dropped their first points of the season on Sunday as West Ham held Maurizio Sarri's team to a 0-0 draw at the London Stadium.
Chelsea had won all five of their Premier League matches before the weekend, going toe to toe with Liverpool, who won again on Saturday to make it six wins out of six.
The visitors dominated possession at the home of their London rivals but failed to create many clear-cut chances and had to deal with West Ham's constant threat on the break.
Olivier Giroud won his battle with Alvaro Morata for a starting spot up front for Chelsea, keeping his place for the second Premier League match in succession.
But Marko Arnautovic, West Ham's leading goalscorer this season, missed out after failing to recover from an injury he sustained against Everton last week.
Chelsea enjoyed more than 70 percent of possession in the first half but West Ham were dangerous when they were able to break out, Michail Antonio proving a real handful.
The home side dealt well with the threat of Willian and Eden Hazard and Giroud - picked for his more physical threat - struggled to make a big impression on the game.
The Frenchman was replaced 20 minutes into the second half by Morata, who went close to breaking the deadlock moments after coming on only to see Lukasz Fabianski pull off a stunning stop from close range.
But with about 13 minutes to go West Ham had a wonderful chance to win the match, when the unmarked Yarmolenko headed just wide at the far post after a cross by Robert Snodgrass.