It is becoming something of an annual examination for Arsenal, a Uefa-invigilated test of Arsene Wenger's ambitions.
Barcelona are the club he regularly cites as the ideal a football team should aspire to. Around this time last year the Catalans clinically exposed the distance left between Arsenal and that summit.
The greatest wonder of a dominant opening 45 minutes in London was the game remained scoreless. With Lionel Messi confusing Arsenal in a then-novel central striker's role, the goals Barca's play merited arrived early in the second half.
Almost preposterously, the Gunners managed to bring the game back to 2-2 by the final whistle, but the Camp Nou was to confirm the obvious. A 6-3 aggregate score captured the long, hard yards Arsenal have to make up.
If both parties go into this evening's rematch complimenting each other as being "better" teams than then, those in Barcelona colours do so from a position of confident superiority.
"Arsenal are a great team. When I watch Arsenal, I see Barca," Xavi said last week. "The difference between them and us is we have more players who think before they play."
For all the wonders of Barcelona's recently ended run of consecutive victories, there is a point at which confidence can catch its possessor out. Xavi and his teammates may be missing the most important difference about Arsenal - that this is a fundamentally altered unit from the team they swept away last year.
The reason Arsenal remain in all four competitions and are the only credible challengers to Manchester United for the Premier League title is not that they have come closer to fitting Barca's template of passing dominance. They are better because they have changed their methods.
There are three elements to the evolution. Two creative, one destructive. First, the team is far more direct, actively moving away from the tantalising, but oft self-defeating, triangular passing that would bring the ball to the opposition's area but not put it in their goal.
This season the team often looks for the quickest route to goal. Cesc Fabregas is the best exponent, regularly picking up possession in his own half and with one look propelling a 50-yard pass to Samir Nasri, Marouane Chamakh or Robin van Persie that places them in on goal.
The variation in tactic troubles opponents and breaks open games.
Chamakh has also helped, offering an aerial target for his teammates capable of converting wing play into headed goals or make long, chipped through balls stick before passing to runners.
At corner kicks, Laurent Koscielny's deceptive movement has added to the set-piece threat Arsenal have been developing for a little while now.
Then there is the devilment that the team have found this season. When Jack Wilshere talks of the "need to get in their faces and be a bit nasty" he is not asking for something unbecoming of Arsenal's current incarnation. For so long derided as the soft touches of the English game, this season they have suddenly turned themselves into aggressors.
The 2009/10 season was a typically gentlemanly one for Arsenal. Only two Premier League sides committed fewer fouls and they almost topped the Fair Play table for fewest cards received. This campaign they are third bottom of the Fair Play league - with a game in hand.
No team has seen more red cards than the six collected so far.
Arsenal have done all this while retaining the best parts of their passing game. They are dirtier, better in the air, and more direct. And they still produce the good stuff.
"We know from the last season's games what is the most important is to play at our level," said Wenger. "Barcelona is maybe better than last year but we are better as well. That will make the game even more interesting."
And it could make that examination result different.
Arsene Wenger v Lionel Messi
The days when a team’s star player got man-marked are a thing of the past, but Messi is one man who needs special attention. He is effectively Barca’s centre-forward, yet tends to float around the pitch. Whether manager Wenger will adjust Arsenal’s tactics is another thing.
Arsenal bear the closest resemblance to Barca of any team in Europe. The middle of the park is loaded with classy ball players like Cesc Fabregas, below, so it could be the strikers who are key. Arsenal’s Robin van Persie is in form and capable of scoring against any defence.
Arsenal recovered from 2-0 down to draw last season’s meeting at the Emirates Stadium. Tellingly, though, they have never beaten Barca in five attempts, including the 2006 Champions League final, when Arsenal led for much of the game before losing 2-1.
Arsenal (4-5-1) Szczesny; Sagna, Djourou, Koscielny, Clichy; Song, Wilshere, Fabregas, Arshavin, Walcott; Van Persie.
Barcelona (4-3-3) Valdes; Alves, Pique, Puyol, Abidal; Busquets, Xavi, Iniesta; Pedro, Messi, Villa
• Arsenal are unbeaten in their last nine home Champions League games, their past defeat being to Manchester United.
• Only twice in the last six years have Barcelona not at least made the quarter-finals, both losses coming to English sides in Chelsea and Liverpool.