Chelsea's 100 percent record in the Premier League came to an end at the London Stadium on Sunday after they were held to a 1-1 draw by West Ham.
Maurizio Sarri's side endured a frustrating afternoon in east London as they bossed proceedings, but couldn't breach the home defence. Andriy Yarmolenko wasted the best chance of the game in the second half as the Blues dropped their first points of the new campaign.
Chelsea settled down quickly at the home of their cross-town neighbours and controlled the opening 20 minutes with possession football.
Their early dominance led to three chances in a short space of time, with Olivier Giroud directing a tame effort straight at Lukasz Fabianski from a driven corner on 10 minutes, before Antonio Rudiger drew a routine save from the Polish keeper from 30 yards out moments later.
Eden Hazard then tested Fabianski with a left-footed shot from 15 yards out on the left after getting away from his marker with some neat touches in the 12th minute.
Mark Noble failed to trouble Kepa on the half-volley from just outside the box on 21 minutes, while at the other end Willian sliced his effort from 25 yards out on the right moments later.
West Ham grew into the game and had the two best chances of the half around the half-hour mark. Felipe Anderson left Cesar Azpilicueta for dead with a silky turn and played in Michail Antonio, who lashed a left-footed shot high and wide of the near post from 10 yards out.
Antonio was presented with an even better opportunity to break the deadlock soon afterwards as Declan Rice released Yarmolenko on the right and the Ukrainian winger drove into the area before being forced wide by David Luiz. The ball fell for the forward, who fired straight at Kepa from five yards out.
N'Golo Kante passed up the final chance on the stroke of half-time when he headed wide of the left post after getting on the end of Willian's volley cross from the right.
Yarmolenko went close on 51 minutes after another powerful run towards goal resulted in him fizzing a strike just over the bar from 20 yards out.
Luiz steered a header high into the stand behind the goal from a 55th-minute corner and substitute Alvaro Morata was denied by Fabianski at close range 11 minutes later after Kante's cross from the right was diverted into his path by the Brazilian defender.
After Luiz aimed a 76th-minute free-kick too close to Fabianski from 25 yards out, Yarmolenko squandered the chance of the match a minute later. Substitute Robert Snodgrass sent a fine cross from the left that the off-season signing nodded wide at the back post with the goal gaping.
Kante again found himself in an advanced area on 81 minutes, but couldn't keep his first-time shot down from Willian's cutback on the left nine minutes from time, and Fabianski capped off another good performance when he denied Ross Barkley a stoppage-time winner with a save at full stretch.