Barcelona vs. Chelsea isn't a "European Clasico" simply because every time they meet, the pitch is decorated with some of Europe's most sumptuous talents. For a fixture to truly sizzle and fizz in the days and weeks before it is played, there needs to be some degree of a revenge or bad-blood narrative, a rivalry that turns an infrequent continental match-up into the kind of "must win at any cost" derby like Milan vs. Inter, Rangers vs. Celtic, Manchester United vs. Liverpool or Madrid vs. Atletico.
This one has all that and more, a fact that can be traced back to an overnight flight back from Moscow to London in early November 2004.
Jose Mourinho's "Blue Machine" had just guaranteed qualification for the knockout round after only four months of his reign and four straight Group H wins. This was when the Special One truly was special. He had back-to-back European trophies with Porto while Chelsea had tripped up, inexplicably, on the verge of the Champions League final the previous season.
Jaunty Jose had the Midas touch, in word and deed. Earlier that night, Damien Duff had set up Arjen Robben for the 1-0 win over CSKA Moscow that guaranteed Roman Abramovich's new European force would reach the last sixteen. Duff, a huge admirer of the modern Barca school, takes up the tale.
"Right from the first moment, Mourinho wanted the draw to pair us with Barca," recalls the brilliant Irish winger. "We were flying back from winning in Moscow and the lads were all just having a bit of fun with Jose.
"We knew we were going to top our group so we were saying: 'Who do you want in the next round boss?' He immediately goes: 'Barcelona!' Our instant response was: 'Are you for real?' But Jose just told us: 'It's simple: We stop them playing and they let us play.' Simple as that as far as he saw it."
Mourinho knew two things. Barcelona, although on the rise, were still the wobbly-legged Bambi of European football. Reborn, but shaky on their feet having not won any trophies for five years and no UEFA title since 1992. They were ripe for a football predator to rip into them.
Secondly, Mourinho knew that in 2004, there was still an ideological war being fought within the Camp Nou. Nominally, Joan Laporta, fueled by his ultra-Cruyffist beliefs, was in charge. But the president had enemies within his board, most notably vice president Sandro Rosell and current president Josep Maria Bartomeu. Those latter two, among others, wanted Barcelona to be pragmatic, mirroring Chelsea by signing big, strong, athletic footballers and to dump Frank Rijkaard so that (future Chelsea coach) Luiz Felipe Scolari could take over.
Mourinho viewed Rijkaard's Barca, where the Ronaldinho-Samuel Eto'o partnership was young but promising and Andres Iniesta had recently been the subject of a hugely fierce debate about whether he should be played or loaned out, as not quite ready to repel his brand of footballing fire and fury.
Essentially, Mourinho was correct. The desire that this quixotic, remarkable, talented and ruthless man has had to inherit the good life as Barcelona coach stemmed from the coaching duties he undertook as understudy to both Sir Bobby Robson and Louis Van Gaal in the late 1990s. And it was evidenced most starkly in the "clasico wars" of 2010-11 when he was Madrid coach in opposition to Pep Guardiola's Barcelona.
But the first time Mourinho caught a whiff of him being able to power his way past a "Cruyffist" Barca and potentially leave himself as the top candidate when the job became vacant was when this rivalry took bitter root back in Spring, 2005.
What followed over the next four matches was a flow of simply extraordinary events, landmark in fact, which set the tone for years of battles between the new, emerging Barca philosophy and the modern Premier League ideal which blended traditional English football beliefs with many of the best imported coaches, players and ideas. A battle that will rage again this week.
Back in 2004 the tone, belligerent and streetwise, was set immediately. Before the match, one Catalan journalist goaded Mourinho about his past as "merely a translator" at the Camp Nou under Sir Bobby Robson and he "bit his head off," nailing what was, quite clearly, a false reputation. Then Mourinho offered to finish the press conference in remarkable style: by naming all 22 players who'd take the field the next night.
First he (correctly) listed the Barca XI before carrying on, "giving away" his Chelsea starting lineup. The move was aimed at taking charge of the pre-match psychology, to tell Barcelona's staff and players "you have nothing I've not anticipated: I'm the boss."
It was fun at the time but better still in the knowledge that he actually fooled his own players.
"I remember Mourinho telling me I was definitely starting but then he played a few 'mind games' with the press," said Duff. "He'd taken me aside and said: 'You are in the team tomorrow but I'm going to give them a different lineup in the press conference. I think he announced Eidur Gudjohnsen was playing instead of me.
"When I saw him name the team on TV, I started believing it and had to wait 24 anxious hours to discover that, lo and behold, I was in it."
Of course, the fun stopped there. Chelsea significantly out-strategized Barcelona: Duff forced Juliano Belletti's own goal and also crossed the ball for the moment when Didier Drogba's challenge on Victor Valdes brought a second yellow and, thus, red card. Eleven men duly beat 10 but Mourinho's accusations of collusion between Rijkaard and referee Anders Frisk led to death threats for the Swedish referee and his retirement out of fears for his family.
The return leg epitomized two schools of football. Barcelona, still delicate and pretty rather than streetwise and the steely competitors they'd become, were blown away by one of the most superb 25-minute power-plays you could ever wish to see.
"Barça were world-class even then but not a patch on what they are now," said Duff. "We gave an incredible performance and it was down to us believing Mourinho when he said that we cold stop them playing."
What about the unpenalized foul Ricardo Carvalho committed on Valdes so that John Terry could head home the winner from Duff's cross once Ronaldinho's hip-shaking goal that shook the world had put Barca in a winning position on away goals?
"Just a little nudge. The dark arts we learned under Mourinho," is Duff's verdict. The fact that Chelsea merited going through back then isn't in much dispute.
Exactly one year later, when paired again, the story was different, but similar. Barcelona had wised up. In winning 2-1 at Stamford Bridge they gave one of their most determined and most impressive away performances ever. Asier Del Horno's horrific lunge with studs extended hasn't prevented Lionel Messi seeing the birth of his third son this week, but it might have done. It was that badly judged, as were Mourinho's words about Messi's reaction being "theatrical."
Then there was born the genesis of what makes Wednesday's tie important not just to discover which previous winner (three of the last seven) emerges, but because it will form a new part of an epic modern dynastic rivalry.
Barcelona and Chelsea had four ties between 2005 and 2006 with two red cards, three own goals, one of Ronaldinho's all-time sublime moments of creative invention, the birth of Messi as a great European power, Mourinho goading the Spanish media and Barcelona as a club, the ultra-controversial retirement of a top quality referee, a total of 14 goals, an owner (Abramovich) who coveted the admiration that went hand-in-hand with beauty of Barcelona's play and Camp Nou board members who coveted the "bigger, stronger, faster" ethos when it came to Mourinho's transfer market outlook.
We, the neutral football lovers, are the beneficiaries of the way this meeting of two ideals has become a European clasico. But I'd also argue that Barcelona have benefitted from Chelsea repeatedly being a thorn in their side.
Can anybody really argue that, over the years, Barcelona signing Eidur Gudjohnsen, Thierry Henry, Eric Abidal, Gerard Pique, Yaya Toure, Seydou Keita, Zlatan, Ivan Rakitic and Luis Suarez hasn't been evidence of the Camp Nou club trying to blend what they cherish most -- technique, passing, control -- with what they fear most, namely pace, power, height, competitive aggression?
Roll up, roll up, roll up: On stage on Wednesday night, the umpteenth episode of a bitter, intense but beautiful and thrilling European clasico. Don't miss a moment.