Fernando Torres rescued Chelsea and Rafael Benitez from FA Cup humiliation as the holders denied Brentford arguably the biggest scalp of all in this season of shocks in a 2-2 draw.
Torres broke his latest miserable run in front of goal with his first of 2013, and one of the most important of his Blues career, to prevent the European champions crashing out of their second competition in five days and sixth in just six months.
It also stopped Brentford becoming the latest lower-league team to upset Premier League opponents this season, something they were seven minutes away from doing after a magnificent performance at Griffin Park, but they have forced a replay at Stamford Bridge.
The League One high-fliers were one in a line of sides to completely outmuscle Chelsea since Benitez took charge, Marcello Trotta firing them in front moments before half-time and Harry Forrester restoring their lead with a penalty after Oscar had equalised.
They might even have clung on had Ross Turnbull been sent off instead of cautioned for conceding the spot-kick, having already been lucky to escape a booking for holding on to the ball in a bizarre repeat of Wednesday's ball-boy incident at Swansea.
As if to drive home the point that their own ball boys had come in peace, Brentford had them form a guard of honour as the European champions took the field, each of them waving a large white flag.
But there was no surrender from the 11 on the field as they tore into a Chelsea side interim manager Benitez admitted may be running on empty.
Running on sand was hardly going to help their energy levels or the passing game Benitez admitted was their only way of playing, but that was exactly the kind of surface that awaited them in what was the archetype of the old-fashioned cup tie.
Ironically, the European champions' millions helped pay for the pitch, as part of an agreement for them to play under-21 games at Griffin Park.
Torres, whose £50million transfer fee could probably buy Brentford Football Club, was recalled.
Fit-again John Terry also started his first game under Benitez but it was almost a nightmare return when Turnbull was penalised for clutching his captain's backpass.
Turnbull's refusal to release the ball for a quick indirect free-kick could hardly have been more ironic in the wake of the Eden Hazard saga, Forrester eventually blazing over the crossbar.
Terry and Turnbull continued to look like strangers, with Chelsea knocked out of their stride by relentless Brentford pressing and lightning breaks.
It almost led to a goal on the half-hour mark when Shaleum Logan won the ball and squared for Adam Forshaw, who drove narrowly wide.
There seemed only one outcome if Brentford could add incision to their industry, and they did just that three minutes from half-time.
Forshaw's sliding tackle robbed Frank Lampard and Forrester unleashed a shot Turbull needlessly parried straight to Trotta, who fired in the rebound.
The Italian delayed his own celebration in fear of an offside flag but the stadium was already in raptures.
Gary Cahill was booked for upending Logan before the break, which saw Marko Marin hauled off and Juan Mata tasked with orchestrating a comeback.
There was plenty of time for Chelsea to get their act together and it took them only 10 minutes to do so, Oscar pouncing on a loose clearance and bamboozling the Brentford defence before drilling into the top corner.
Mata almost finished off a sweeping move and Lampard's header from a corner was kept out by Simon Moore as the visitors began to show the kind of fight completely lacking in the first half.
But Brentford refused to panic, drawing Chelsea's sting before withdrawing Trotta for Tom Adeyemi with 20 minutes remaining.
It was inspired, the substitute winning a penalty almost immediately after being upended by Turnbull racing on to Clayton Donaldson's brilliant through ball.
Turnbull might have seen red but escaped with a booking before Forrester buried the spot-kick right in the bottom-left corner.
Chelsea briefly laid siege to the home goal, Branislav Ivanovic denied by Moore before being taken off for Cesar Azpilicueta.
Forrester followed for Scott Barron with Demba Ba finally arriving for Ryan Bertrand, who had just wasted a glorious headed chance to equalise.
Ba made the difference, challenging for an 83rd-minute ball that fell to Torres, who instinctively curled it into the top corner from 18 yards.
Lampard went close to a winner and Mata appealed furiously for handball in the box against Harlee Dean but that would have been a travesty of justice.
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