Steven Pienaar and Denis Stracqualursi struck as Everton piled on the pressure for Chelsea manager Andre Villas-Boas with a 2-0 victory.
Pienaar celebrated his Goodison Park return by firing the Toffees into a fifth-minute lead on another dismal Barclays Premier League afternoon for Chelsea and Stracqualursi doubled the advantage in the second half.
The defeat left Chelsea without a win in four league games and was another setback in their bid to retain a top-four place.
Fernando Torres' dismal season also continued as he again struggled in front of goal and there was further bad news as Ashley Cole limped off.
Chelsea were punished after five minutes when Frank Lampard deflected a Tim Cahill ball over Branislav Ivanovic's head. Pienaar raced into the box, controlled the bouncing ball on his chest and smashed past Petr Cech into the roof of the net.
Chelsea were inches away from an equaliser as Daniel Sturridge met a low ball from Juan Mata, which Torres cleverly allowed to run across the edge of the area, with a firm shot but it was deflected over by Phil Neville.
Mata caused further problems for the home defence as he pulled the ball back for Lampard but he dragged his shot wide from 18 yards.
After the break Villas-Boas sent on Florent Malouda for Michael Essien, but the change did not appear to be appreciated by all visiting fans.
Everton doubled their lead 18 minutes from time after Neville won the ball in midfield from Cole and released Landon Donovan. The American ran at the defence and then flicked a fine ball into the path of Stracqualursi, who calmly wrong-footed Cech to score.
Cole remained on the ground after the challenge by Neville and, after the restart was delayed while he received treatment, he was unable to continue to further sour Chelsea's day.