A below-par Chelsea was condemned to a 1-0 defeat by Bournemouth after VAR intervention awarded a Dan Gosling late strike.
The London Blues were looking to extend the lead between themselves and the top-four chasing pack after making way to the last-16 of the Champions League.
Mason Mount had the first big chance at goal after chesting down a cross from full-back Cesar Azpilicueta only for his shot to be stopped by Aaron Ramsdale.
Tammy Abraham also came close minutes later, swinging a volley into the side of the net.
Neither side could produce a shot at goal in the first 15 minutes after the interval, but the visitors missed perhaps their best chance of the game when Josh King’s square ball missed Lewis Cook by some distance.
Lampard switched Pulisic and Willian for Callum Hudson-Odoi and Matteo Kovacic but none could influence the result.
Hudson-Odoi gave the defenders a lot of work to do though after his cross caused some havoc in Bournemouth’s box. After a series of headers, the ball dropped to Emerson who just couldn’t find the net.
That miss would however prove costly because the visitors got the winning goal with only six minutes left on the clock to play.
Jefferson Lerma’s header found Dan Gosling in the box and with the player’s back to goal, he dinked it over Chelsea’s goalie who clearly didn’t expect the shot.
The flag was raised for offside but after a VAR review showed Gosling to be onside, the goal was allowed to stand.
The Blues were really terrible and failed to truly test Bournemouth’s goalie other than a long-range shot from substitute Kovacic in the final minutes of the game.
With this loss, Chelsea have now fallen to their second home defeat in three league outings.