Chelsea lost more ground on the top four as West Ham battled back to earn a point at the London Stadium.
A fast start from the Blues saw Joao Felix have a goal disallowed on his second Blues start, before the Portuguese fired the visitors in front from Enzo Fernandez's fine cross.
Kai Havertz then put the ball in the net again only for it to be disallowed, before ex-Blues left-back Emerson popped up at the back post to level after a Jarrod Bowen flick-on.
