A poor result that doesn't help our hopes for a top-four finish, but in truth, our performance merited little else.
Having fallen behind to Steven Pienaar's fourth-minute strike, we struggled to impose ourselves on the game, with Everton Goalkeeper Tim Howard having a fairly comfortable afternoon.
Denis Strasqualursi scored a second for the home side midway through the second half, and it was a goal we never really looked like recovering from.
Our first defeat of 2012 leaves us with plenty of work to do, but with a fifth round FA Cup tie at home to Birmingham next week, the reaction will need to be instant.
Andre Villas-Boas was able to welcome back Frank Lampard from injury, with the midfielder captaining the side in John Terry's absence. Gary Cahill dropped to the bench following his debut last weekend, with Branislav Ivanovic partnering David Luiz in central defence and Jose Bosingwa reverting to right-back. Ashley Cole, meanwhile, returned to the side after missing the Manchester United game last week through suspension.
After a cagey opening, Everton took the lead with the first real attack of the game in the fourth minute when Lampard's attempted clearance fell kindly into the path of the onrushing Pienaar, who controlled with his first touch and fired past Petr Cech to give the home side the lead.
The move had started from a careless Bosingwa throw-in which fell straight to the feet of Tim Cahill, which made the goal all the more difficult to digest for the travelling Blues supporters.
A teasing cross from Phil Neville shortly after looked to be causing the Blues another problem, but Strasqualursi's header sailed wide.
Fernando Torres, who was unsurprisingly booed by the home crowd due to his Liverpool connections, attempted to create an opening after being released down the right by Bosingwa, Sylvain Distin recovered well though and cleared the danger.
It was a sloppy start by the visitors and Cech saved well from a fizzing Landon Donovan effort in the 18th minute as the hosts looked to double their advantage.
Slowly, we began to raise the tempo, with Mata in particular pulling the strings, and Daniel Sturridge almost equalised when he met the Spaniard's cross with a fierce left-foot drive which was deflected over.
Lampard then fired past Howard's left-hand post as a Mata cross, which was intended for Torres, fell into his path, and the skipper's frustration with himself was clearly apparent as he has scored from similar positions so often in the past.
Pienaar then linked up well with Leighton Baines in order to create an opening for Tim Cahill, but the Australian couldn't get the ball under control and Cech was able to come and gather.
Howard, usually an accomplished and confident goalkeeper, was looking vulnerable at coming for crosses and, following his earlier mistake, almost spilled another Mata delivery, but we had only ourselves to blame for failing to capitalise on a number of set-pieces from dangerous positions.
With the clock ticking towards half time, Torres did well to meet Bosingwa's cross, but a lack of pace on the delivery meant his effort was never realistically going to trouble Howard, while a minute later the Spanish striker looked to have a legitimate penalty claim waved away.
Both managers opted not to make any changes at the break, though if Villas-Boas was looking for an immediate reaction from his players there was none forthcoming, with our build-up play all too often slow and predictable.
Torres became the third Chelsea player to enter referee Mike Jones's book, after Meireles and Bosingwa, when he was adjudged to have tripped Pienaar, much to the delight of the home crowd.
Lampard then released the advancing Cole down the left-hand side, but the defender's delivery was easy for Howard to deal with.
Tempers were beginning to fray on both sides, with Ivanovic and Donovan fortunate to escape bookings following a spat which started after the Blues defender fell into the advertising hoardings behind our goal.
Neville's challenge on Cole, who had lost control of the ball, ran into the path of Donovan, and when the American slipped in Strasqualursi, the striker calmly slotted his effort past Cech to send the home supporters delirious.
Bertrand crossed to the back post as the Blues pressed forward and as Sturridge headed towards goal, Lukaku's effort was blocked by Howard.
Everton continued to threaten on the break as we poured forward in desperation for a goal that would offer a glimmer of hope, but it failed to materialise as we slumped to our first defeat of the year.
Chelsea (4-3-3): Cech; Bosingwa, Ivanovic, David Luiz, Cole (Bertrand 76); Meireles, Essien (Malouda 68), Lampard (c); Sturridge, Torres, Mata (Lukaku 77).
Unused subs: Turnbull, Ferreira, Cahill, Mikel.
Booked: Meireles 41, Bosingwa 51, Torres 58
Everton (4-4-1-1) Howard; Neville (c), Heitinga, Distin, Baines; Donovan, Gibson (Hibbert 88), Fellaini, Pienaar (Drenthe 74); Cahill; Stracqualursi (Duffy 90+3).
Unused subs: Mucha, Barkley, Gueye, Vellios.
Scorers: Pienaar 4, Strasqualursi 71
Referee: Mike Jones