Both sides started the game as they intended to go on, with Chelsea seeing most of the ball but the home side looking comfortable and ready to counter-attack, and it was through that strategy that Brentford almost opened the scoring. Ramires gave the ball away in midfield which led to a sweeping counter-attack that Marcelo Trotta wasted with a wild finish.
Brentford soon had another opportunity to take the lead after Ross Turnbull picked up John Terry's backpass - the Bees were duly granted a free-kick just inside the penalty area, but Harry Forrester blazed it over. It was a series of incidents for Turnbull which made the Chelsea keeper appear ill-at-ease, and he was soon responsible for Brentford taking a remarkable lead. Harry Forrester's 25-yard drive was only parried by the keeper, and Marcelo Trotta had followed up to smash the ball home and send Griffin Park wild with delight.
The second half began in surprisingly open fashion, and with the tempo of the game always likely to favour Chelsea, they soon equalised through a wonderful goal from Oscar. producing a superb touch to control a cross from the left and slot the ball home from inside the area.
Incredibly, Chelsea were to find themselves behind again - and Ross Turnbull was once again culpable for the Blues, charging out at Tom Adeyemi and giving away a penalty. It was a debatable decision - there was little if any contact, although it certainly wasn't a dive - but Harry Forrester stepped up to convert his penalty and leave Chelsea staring down the barrel with 17 minutes remaining.
The visiting Chelsea fans had been on Rafael Benitez's back all afternoon, and that did not improve when, with Demba Ba still languishing on the bench, the Chelsea boss instead opted to swap Branislav Ivanovic with Cesar Azpilicueta. Eventually, however, Demba Ba was introduced - although surprisingly, on the left-wing, and the Senegalese striker soon made his presence felt, winning the ball on the edge of the area and finding Fernando Torres, who swept home to level the scores late on.
The match will now go to a replay, with Chelsea having avoided a humiliating exit, but not entirely avoided embarrassment.