Chelsea host Barcelona three years on from one of the European football's most dramatic and controversial evenings.
Tom Henning Ovrebo, the Norwegian referee, turned down three penalty appeals from the Blues in the 2009 Champions League semi-final second leg, before Andres Iniesta hit Barca's first shot on target to score and send them through on away goals.
But another penalty shout was rejected, which compelled a seething Michael Ballack to chase the official while an enraged Didier Drogba labelled Ovrebo's refereeing a "f*****g disgrace" on live TV after the final whistle.
Four appeals, no penalties
Thirteen times these two teams have faced each other (check out our gallery dating back to their first meeting in 1966), and scuffles between the pair occurred even 46 years ago.
Since the turn of the century, the pair have met 10 times in the Champions League, dating as far back to the Gianluca Vialli era at Stamford Bridge.
Chelsea beat Barcelona 3-1 in the first leg at the 1999/00 quarter-final stage, in which current Blues and Barca bosses Roberto di Matteo and Pep Guardiola battled against one another in midfield. The Londoners were thrashed 5-1 at Camp Nou in the return fixture, and had Celestine Babayaro sent off.
Barcelona 5-1 Chelsea, 2000
But tempers truly frayed during Jose Mourinho's tenure in west London. Under Vialli, Chelsea were European Cup novices, having taken the Football Association's advice not to participate in the inaugural competition back in 1955. Under Mourinho, fresh from guiding surprise package Porto to their second European Cup in 2004, they were contenders.
Mourinho was a translator at Barca under Bobby Robson, before he upgraded into the role of coaching assistant to Louis van Gaal. And there was no love lost between him and his former employers, particularly after Chelsea lost 2-1 in Catalonia, with Didier Drogba controversially sent off.
Disgruntled at the Ivory Coast international's dismissal, players, supporters and most vociferously, Mourinho, castigated referee Anders Frisk for his decision. Less than a year previously, Frisk was branded a "homer" by Ruud van Nistelrooy after Holland lost to Portugal at the 2004 European Championship, and he was now facing similar accusations.
Mourinho publicly accused Frisk of having invited the Blaugrana manager, Frank Rijkaard, into his changing room at half-time, an which Uefa regulations prohibit.
Chelsea 4-2 Barcelona, 2005
Uefa charged Chelsea with inappropriate conduct following the match, while their Portuguese coach received a touchline ban. It was revealed on 7 April that the Uefa venue director, Pascal Fratellia, witnessed Rijkaard say hello in the tunnel and then attempt to converse with Frisk about the. Allegedly Frisk told him: "This is not the place or the moment to talk about the match."
The Swede however received death threats from Chelsea fans and retired from refereeing with immediate effect two weeks later. Mourinho meanwhile was branded an "enemy of football" by Uefa referees committee chairman Volker Roth.
Despite the controversy and a 2-1 defeat in Spain, Chelsea qualified for the quarters via a 4-2 win in London. Much to Mourinho's unrestrained delight.
The pair met again at the same stage the following year when more controversy occurred. Lionel Messi, then just 18, appeared to feign agony to ensure the sending off of Blues left-back Asier del Horno during Barca's 2-1 win at Stamford Bridge. Mourinho suggested the Argentinian was "play-acting", and Chelsea could only draw the second leg as they were eliminated.
Three years later, Chelsea were in command for the majority of the 180 minutes played between the two teams, with the exception of that stoppage-time strike Iniesta stroked home, scuppering chances of a second successive Manchester United-Chelsea final.
Chelsea 1-1 Barcelona, 2009
Since then, Barcelona have won two European Cups in three years whereas Chelsea, a width of a post away from their first the previous year, are still searching for the elusive "big ears".
But here are five reasons for Blues optimism ahead of tonight...
11 ANGRY MEN
Still at the club, Petr Cech, Jose Bosingwa, Ashley Cole, John Terry, Frank Lampard, Michael Essien, Florent Malouda and Didier Drogba all started the second leg of that semi-final second leg three years ago. Although they may stress otherwise, vengeance will be utmost on their minds, while Branislav Ivanovic, John Obi Mikel and Salomon Kalou watched on helplessly from the bench on Wednesday 6 May 2009.
Juan Mata explains the significance of tonight's game:
POPPING THE CHAMPIONS LEAGUE CHERRY
Relics of the Mourinho era they may be, but some squad members are desperate to win the Champions League. As selfish and risible the player power culture at Chelsea is, the goal of becoming European champions for the first time brings out their selfless side. Time is running out, but the likes of Terry, Lampard, Drogba and Cole's European ambition can be gauged by just how gutted they looked three years ago, and when they lost the final in Moscow in 2008.
DROGBA
Even prior to his exhibition in bullying against Tottenham at the weekend, Chelsea should have tied down Drogba to a new contract by now. He was awesome in the round-of-16 comeback against Napoli, and despite a profligate campaign last season, at 34-years-old he has shown tremendous appetite to continue performing on the biggest stage. He scored a memorable winner against Barcelona in the group stages five-and-a-half-years ago, and has invariably troubled their suspect defence.
Ex-Chelsea boss Ruud Gullit is now on Twitter:
BARCA'S ANGLOPHOBIA
Yes, they have beaten United in two finals in two years - one coming at Wembley - but Barcelona's record on English soil is decidedly mixed. Their last win in England - excluding last year's one-sided final - was in 2007 at Anfield, and even that 1-0 win was not enough as the Champions League holders bowed out on away goals to Liverpool.
Since then they have lost to United in the 2008 semi-final, drawn at Chelsea the following year, and in successive seasons played Arsenal twice at the Emirates, drawing 2-2 and losing 2-1. Overall they have won seven matches from 19 at English stadiums against English opposition. (They won the 1992 European Cup at Wembley against Sampdoria.)
Cesc Fabregas is pleased to be back in London:
POWER PLAY
Appreciating Barcelona's majesty can be a challenge, such is their penchant for play-acting in a bid to con referees (usually successfully), but Chelsea have no choice but to use their grit to exploit their opponents' brittleness.
Cesc Fabregas said at the pre-match press conference how the Blues' improvement under Di Matteo has coincided with them adopting the style of play which made them "great" under Mourinho. They are an inferior side than Barcelona, but their bulldog style is essential if they are to beat them over two games. That Barca tend to whinge if a gust of win fells one of their own suggests they are vulnerable to physicality in football.