Former Chelsea defender Emerson Palmeri scored an equaliser to deny his former club as West Ham drew 1-1 in the Premier League at the London Stadium.
Chelsea had two first-half goals disallowed. The first from Joao Felix and another from Kai Havertz but the Blues will not be denied a third time as Felix latched onto a delicious cross from record signing Enzo Fernandez.
But the Hammers hit back thanks to a Jarod Bowen header that was attacked by Emerson who beat ball-watching Noni Madueke to score.
In a second half of few chances, Tomas Soucek put the ball in the back of the net in the 82nd minute but Declan Rice, who headed the ball on to the Czech, was ruled offside by VAR.
A few minutes later, Chelsea appealed in vain for a penalty, claiming substitute Conor Gallagher’s shot was stopped by Soucek’s hand.
The draw meant Chelsea have now won only one of their last seven league games – and they have not won away since October. They stayed ninth in the table, nine points behind fourth-placed Newcastle who have played a game less.
Chelsea coach Potter said he saw positives in the performance of his players, especially in the first half when the Blues, as well as scoring through Felix, had the ball in the back of the net twice but both were ruled out for offside.
“It was a step forward for us in terms of the previous game and lots to go forward with,” he told BT Sport.
“We had real control of the game and it was a cheap goal from our perspective. That lifts the crowd and makes it more difficult but that is something we have to manage better. We will get better from the experience.”
West Ham climbed up to 15th but are only two points ahead of Everton, the highest placed team in the relegation spots.
West Ham manager David Moyes said he was happy that his side survived Chelsea’s early dominance.
“If you had given me a point after 20 minutes I’d have shook your hand and walked away. We didn’t start well and they were good but we made some basic errors defensively,” Moyes told the BBC.
“I was hoping it was going to be our day but we had a couple of close calls as well. We take the point and it keeps a bit of a better run going right now.”