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 by securing 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.
The npower 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.
Fit-again John Terry started his first game under Benitez but it was almost a nightmare return when Turnbull was penalised for clutching his captain's backpass, but Forrester blazed 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.
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.
Substitute Juan 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. Demba Ba came on for Ryan Bertrand and made the difference, challenging for an 83rd-minute ball that fell to Torres, who instinctively curled it into the top corner from 18 yards to force a replay.