Southend 1 Chelsea 4
Luiz Felipe Scolari's Chelsea survived the fog and a potential upset as they came from behind to see off spirited League One outfit Southend 4-1 in their FA Cup third-round replay at Roots Hall.
The under-pressure Blues manager laid into his players for some recent below-par performances, which culminated in the 3-0 capitulation at Manchester United.
With the Red Devils having now moved above Chelsea in the Premier League following their win over Wigan tonight, the Brazilian coach knew another slip-up against the Shrimpers would lead to further testing questions as to his reign.
However, after the match was initially called off by referee Chris Foy as fog had descended on the Essex coast, only to be reinstated as the conditions improved, for a spell it seemed as if another upset was on the cards when captain Adam Barrett headed the home side in front from a corner which made a mockery of Scolari's new zonal marking system.
Goalkeeper Petr Cech produced a stunning reaction save at point-blank range from Alex Revell, which would prove to be the key moment of the tie.
Because on the stroke of half-time, German Michael Ballack drilled in a fine equaliser following a mix-up in the Southend defence, and from then on, there only looked one winner.
Salomon Kalou - in the starting line-up at the expense of the axed Didier Drogba, a reported transfer target for Jose Mourinho's Inter Milan - put the Premier League side in front with a well-worked effort on the hour, before Nicolas Anelka wrapped things up 13 minutes from time with Frank Lampard adding a fourth in stoppage time.
Coca-Cola Championship side Ipswich await in round four, and you suspect a few more obstacles for Scolari and his men between now and May.
Chelsea made a lively start as Kalou burst into the penalty area down the left, and got to the touchline before cutting the ball back across goal and Ballack's shot was blocked.
Joe Cole was then put in down the right by Lampard, but his low shot hit the legs of Southend goalkeeper Steve Mildenhall and was cleared.
Set-pieces have proved Chelsea's undoing in recent games - and was again their Achilles heel as the hosts snatched a shock lead on 15 minutes.
Junior Stanislas, on loan from West Ham, sent over a corner, which the visitors failed to deal with and Barrett arrived on cue at the far post to power a header into the net.
Chelsea immediately went on the offensive, and it needed a desperate clearance from Anthony Grant in front of his own goal to prevent a certain equaliser.
Chants of "you are getting sacked in the morning" rang out around Roots Hall, with Scolari looked less than impressed at his team's efforts.
Mildenhall produced a superb reaction block to deny Lampard from point-blank range, with Cole's follow-up shot blocked and Ballack driving the loose ball over.
Ballack saw his shot on the turn deflected behind as another chance went begging before the German sent a 20-yard volley just over the bar as the one-way traffic continued.
However, Southend almost snatched a second on the break.
Foy played a superb advantage after John Mikel Obi had flattened Grant, with the ball played out to Stanislas on the right.
His looping cross floated over to the far post, where Revell arrived at pace, but somehow Cech kept out his bullet header and Franck Moussa blazed the follow-up over.
The referee then called the Chelsea midfielder back, and showed him a yellow card.
Just when it seemed Southend would go into the break ahead, Chelsea grabbed an equaliser.
A high ball into the penalty area caused confusion between Peter Clarke and his goalkeeper, with the half-clearance dropping to Ballack.
The German needed no second invitation - and crashed a stunning half-volley into the top left corner.
Chelsea started the second half well, as Ashley Cole drilled in a low effort from 20 yards, which Mildenhall pushed out at full stretch and Southend scrambled the ball clear.
Chelsea finally got themselves in front on the hour mark.
Joe Cole showed some neat footwork to release Kalou on the right, and the Ivory Coast forward drifted past two defenders before drilling a low shot into the far corner.
The goal killed the atmosphere for the home fans packed inside Roots Hall.
Cole was then forced off with a what looked like a knee problem, to be replaced by Franco di Santo, the former West Ham man grimacing in pain as he hobbled off.
Chelsea wrapped things up with 13 minutes left when Kalou and Lampard created space for Anelka to run into the box and he made no mistake from 12 yards before Lampard rubbed salt into the wounds to net a fourth after a breakaway in stoppage time.