Chelsea surrendered a lead against Brighton for the second time in a month as both sides had to again settle for a 1-1 draw on Tuesday.
The European champions went ahead against the run of play when Hakim Ziyech’s snap shot caught Robert Sanchez in the Brighton goal by surprise.
But the Blues have now just won one of their last seven league games as Adam Webster’s towering header earned Brighton a fully deserved point.
Thomas Tuchel was critical of his forward players after a 1-0 defeat at Manchester City on Saturday, but kept faith with Romelu Lukaku and Ziyech in attack as Timo Werner and Kai Havertz were again left on the bench.
There was little to impress the German once more as Chelsea’s slump leaves them looking over their shoulders at the contenders for a top-four finish rather than a title challenge.
They remain third in the table, 12 points behind leaders Manchester City having played a game more.
Brighton have only won twice in their last 16 league games, but once again just lacked the cutting edge to their impressive build-up play.
After a bright opening, the hosts were hit with a sucker punch when Ziyech justified his inclusion with a powerful low effort that Sanchez should have done better to save down to his left.
Callum Hudson-Odoi wasted a great chance to double Chelsea’s lead just before the break when he was put through by Lukaku in one of the Belgian’s few productive moments.
Brighton were again faster out of the blocks after half-time and Kepa Arrizabalaga did brilliantly to turn Alexis Mac Allister’s deflected shot onto the post.
But Chelsea’s reprieve did not last long as from the resulting corner, Webster was given a free run to power home from Mac Allister’s cross.
Lukaku had Chelsea’s one clear chance to retake the lead when Sanchez made amends for his earlier error by blocking the ball into the side-netting.
Chelsea’s record signing was then replaced as Tuchel turned to his compatriots Havertz and Werner for the final quarter.
The German international duo were just as ineffective as Brighton held out comfortably and could even have snatched all three points with more composure on the counter-attack.
Chelsea host Tottenham on Sunday in their final league game for nearly a month due to an international break and their commitments at the Club World Cup in February.
Should Tuchel’s men fail to turn things around at Stamford Bridge, they could return from Abu Dhabi with their place in the top four under severe threat as the chasing pack make up their games in hand.