Fog briefly put this tie in doubt, just as clouds of uncertainty had clung to Scolari's reign. First the fog, then the clouds around Scolari were dispelled, leaving Chelsea's manager, and his board, breathing more easily. But Scolari will never forget his visit to Southend, his emotions put through the wringer as Roots Hall screamed itself hoarse. When Adam Barrett, Southend's outstanding captain, gave Steve Tilson's gutsy side the lead, the pressure mounted on Scolari.
With his team trailing, and seemingly all of Essex baying for his blood, here was a real test for Scolari. "You're getting sacked in the morning," chanted the locals. This was noisy nonsense. Even if Chelsea had faltered, the word from Chelsea's powerbrokers remained the same: they would continue to back their coach because, unlike Avram Grant last season, Scolari owns a CV that earns him respect and time.
To the relief of watching Chelsea dignitaries like Peter Kenyon and Bruce Buck, Scolari's players responded to adversity, pouring forward time after time, pinning Southend deep in their own half, and hitting back with Michael Ballack's magnificent equaliser before the break. Salomon Kalou, Nicolas Anelka and Frank Lampard struck in the second period to set up a fourth-round date with Ipswich Town.
Scolari had sought "answers" from his players after all the questions raised by their frailties in recent days, most notably in Sunday's humiliation at Old Trafford. Answers were provided here: this starting 11 played for their manager, played for the shirt.
No Didier Drogba, no problem. Left behind in London, the Ivory Coast international was known to feel victimised by his demotion by Scolari, apparently resenting the perception that he was responsible for Sunday's humiliation.
Chelsea have let Drogba know that if he really wants a move, he will need to start putting on more assertive displays than his widely-derided contribution at Old Trafford. Drogba will not be allowed to leave cheaply either. Along with Drogba, Deco was also held accountable for Sunday's embarrassment, his lack of mobility exploited by Manchester United and now punished by Scolari. Neither player was missed.
But before John Terry, Lampard and Ballack could show their mettle, they were ambushed. After the fog had lifted, Scolari and his side had swiftly seen the shape of the challenge at Roots Hall. Southend fans, all singing, all flag-waving, screamed at every Chelsea touch, particularly when the ball was in the possession of Ashley Cole, that embodiment of Premier League arrogance. When Chelsea's other full-back, Jose Bosingwa, slid into the hoardings, the Portuguese international received some choice Essex invective.
Fuelled by the fire of their supporters, Southend players snapped into tackles, giving their illustrious guests no space to breathe, let alone create an opening for 44 minutes. Their tactics frustrated Chelsea for most of the half, Alex Revell and Lee Barnard taking it in turns to drop off the front line and stiffen midfield.
The determination etched on Revell's face as he hunted down Ashley Cole said everything for Southend's commitment levels. They sensed an upset. They had read all the stories of trouble at the Bridge, had seen how Chelsea waved the white flag at Old Trafford. Tilson's players craved this chance of writing them names in FA folklore. Chelsea had other ideas.
But they need more ideas at defending set-plays. Junior Stanislas, a livewire presence, whipped in a 15th-minute corner that caused carnage, allowing the unmarked Barrett to head in. Chelsea's defence seems trapped in a recurring nightmare: seven of their last eight goals conceded have emanated from freezing at set-pieces.
The heat was on for Scolari. Emerging from the dug-out, he barked a few instructions to his wide players to hug the flanks more, so stretching Southend's packed midfield, anything to create some space so Lampard and Ballack could pierce the armour-plated centre.
So the great revival began. Lampard, tireless in midfield, was denied by Southend's keeper, Steve Mildenhall. Ballack shot over, then wide. Still Chelsea attacked. Still Southend breathed defiance, Barrett proving the rock on which Chelsea foundered. Lampard, embodying the visitors' hunger and attacking intentions, swerved in a corner that Terry headed over.
So committed to attack, Chelsea were vulnerable to the counter. After Chris Foy had played an inspired advantage when John Obi Mikel took out Anthony Grant, Stanislas raced down the right, his acceleration catching out Ashley Cole. Stanislas' cross was perfection, weighted to reach the stooping Revell at the far-post. Cech kept Chelsea in the Cup with a stunning, whites-of-the-eyes save.
Reprieved, Chelsea stormed back the other end, equalising just before the interval. When Mildenhall and Barrett collided, the ball fell to Ballack, whose response was sensational. The German international has deserved his criticism this season, a heavyweight performer punching far below his weight, but he merits huge praise here. He had no time to think, no split-second to waste. Meeting the loose ball first-time, Ballack swept it into the net from 15 yards.
Joe Cole began to make an impression for Chelsea, thwarted by Mildenhall, but then sweeping a magnificent pass from left to right. Kalou darted on, driving into the box before shooting low past Mildenhall.
The tie was wrapped up when Lampard and Kalou combined to set up Anelka, who struck from 10 yards. Lampard, with a late shot, completely blew away the fog draped like a dark veil over Chelsea. But with Stoke City up next, Scolari has more work to do on that zonal marking.
FA Cup fourth round draw:
Liverpool v Everton Manchester United v Tottenham Hotspur Hull City v Millwall Sunderland v Blackburn Hartlepool v West Ham Sheffield United v Charlton Athletic Cardiff City v Arsenal Portsmouth v Swansea City Chelsea v Ipswich Town Cheltenham Town or Doncaster Rovers v Aston Villa West Bromwich Albion v Burnley Torquay United v Coventry City Kettering Town v Fulham Watford v Crystal Palace Derby County v Nottingham Forest Wolverhampton Wanderers v Middlesbrough