Chelsea were narrowly beaten 1-0 against Everton in the Premier League on Saturday at Goodison Park.
A day to forget for the Blues in Merseyside as they were unable to take top spot, missing several excellent chances to take points back to London.
Gylfi Sigurdsson scored the only goal of the game after giving Everton the lead in the 22nd minute, cooly slotting away from the penalty spot after Dominic Calvert-Lewin was brought down in the area.
Chelsea broke inside the first two minutes as Timo Werner led a Chelsea attack. He cut it back to Kai Havertz, neither opted to shoot, and the German's poor pass was cut out by Ben Godfrey.
Richarlison had a good chance for the hosts in the seventh minute after playing a one-two with Gylfi Sigurdsson, but his effort from close range was extremely tame and straight at Edouard Mendy.
Mendy gave the visitors a scare when he landed awkwardly after collecting a Sigurdsson free-kick, but he was able to continue, thankfully for the Blues.
But Mendy made a needless foul in the 21st minute on Dominic Calvert-Lewin inside the box which saw Carlo Ancelotti's side take the lead as Sigurdsson cooly converted, sending Mendy the wrong way in the 22nd minute.
Reece James nearly levelled in the 26th minute as a corner fell to him on the edge of the area, but Jordan Pickford made an outstanding save to tip it onto the post.
Chelsea were knocking and Kurt Zouma was the next to have a great chance two minutes later. Olivier Giroud headed it down but the Frenchman could only hit it straight at Pickford from eight yards out.
Richarlison had another excellent chance to double the lead five minutes before half-time, but Mendy saved well with his feet to avert the danger.
Mason Mount went close to levelling inside the first two minutes of the second-half, but his lob from distance over Pickford hit the crossbar and went over.
Richarlison had another tame effort saved as the hosts broke five minute later. Yerry Mina had a chance for the hosts but he headed over at the back post.
Sigurdsson fired a free-kick just over the bar in the 54th minute which Mendy was left flat-footed and was well-beaten if it were on target.
Everton thought they had another penalty in the 63rd minute when Calvert-Lewin went down in the box, but VAR overturned Jonathan Moss' initial decision for offside.
Tammy Abraham was introduced by Frank Lampard to try to change the course of the game for the Blues; Kai Havertz' disastrous evening was ended.
Reece James was Chelsea's best performer and he made an excellent defensive recovery to win the ball off Richarlison, who was running straight on goal with 15 minutes to go.
Chelsea were denied by the woodwork again as Mount's free-kick in the 81st minute hit off the post after sending Pickford the wrong way.
Billy Gilmour was brought on in the final stages for Mateo Kovacic as Lampard's side continued to search for an equaliser.
The Blues kept on churning out chances and Giroud was the next after Werner found him with a low cross in the box, but the Frenchman could only fire over.
But the Blues were unable to find an equaliser and Sigurdsson's first-half penalty was enough to hand Ancelotti's side all three points.
One of the Blues' worst performances, if not the worst performance to date this season.
A 17 game unbeaten run and an unbeaten away record in the league brought to an end.
Chelsea will need to dust themselves off quickly for the trip to Molineux to face Wolves on Tuesday.