The hurt may be greater than it was in the 4-1 trouncing here last season, because this was a tie that might have taken a different course. Arsène Wenger's side, with the score at 1-1, held a 3-2 aggregate lead when Robin van Persie was sent off in the 56th minute for a second booking. The referee Massimo Busacca was sure he had played on intentionally and had a rare shot at Barcelona's goal instead of simply failing to hear the whistle.
Patronising though the appraisal will sound, Arsenal were far closer to Barcelona. There is, despite that, an obligation to emphasise that they posed so little threat that there was not a single shot on target for Víctor Valdés to save. In the circumstances, Wenger has to settle for notable evidence that Arsenal do have a durability now that will be valuable in the bid for the Premier League title.
While prospects look appealing on that front, nothing came easily for the side in this fixture. The young goalkeeper Wojciech Szczesny lasted 19 minutes and had to go off after a seemingly mild shot by Daniel Alves bent back a finger, later confirmed as dislocated. His replacement was Manuel Almunia. The Spaniard's presence took to six the number of Arsenal players on the pitch who had been in the starting line-up here last season.
Circumstances beyond the control of Wenger have made some of the changes inevitable, but Arsenal's unsettling search for a first trophy in six years also contributes to the restlessness. Some of his verdicts are being vindicated. The defensive midfielder Denílson has been downgraded to the Carling and FA Cups. He started at the Camp Nou last season but did not leave the bench in this match, even though the current defensive midfielder Alex Song was injured.
Abou Diaby took up some of those chores although he is not a specialist in that work. It was still a comparatively subdued first half, putting aside the fouls that led to four of the Arsenal line-up being cautioned. There was just a moment to spare for real distinction, then, as Messi struck in the third minute of stoppage time before the interval. Cesc Fábregas attempted a flick and gave possession to Andrés Iniesta. The through pass put Messi clear and he dinked the ball over Almunia, who was attempting to dive at his feet, before thumping it gleefully into the net.
For all that gusto, Barcelona were, by their own measure, judicious. Pep Guardiola, left with more regard for Wenger's squad after the 2-1 defeat in London, had rested some of his men in the weekend victory over Real Zaragoza. Energy was particularly significant against Arsenal, who had decided to hold a high line at the Camp Nou rather than back off and leave the opposition with simple possession.
It was Guardiola's men who looked better-equipped to set up a goal. If there is one area of reconstruction in which Wenger is starting to take a tentative pride it is in a defence that has a good record and the manager is entitled to note this achievement. Given the context, the relapse into folly for the opener must have been all the more distressing.
Arsenal, behind on the away goals rule, had no alternative but to revert to their true selves and take the game to the opposition. Barcelona would have felt at ease with that. Guardiola's team emerged from the interval with greater confidence but it was soon undermined in peculiar fashion.
Samir Nasri's persistence earned a corner on the left. The midfielder flighted it over and Diaby's run seemed to distract the defence so severely that Sergio Busquets, a midfielder employed at centre-half because of injury and suspension, headed into his own net. Arsenal, though, suffered, too, when the second booking followed for Van Persie, who claimed he did not hear the referee's whistle above the noise in the crowd.
Even so, Wenger's men, with their lead in the tie, were more at peace for a time than Barcelona. Guardiola's side and the home support all knew that a goal was essential to take the game to extra time. Almunia was outstanding in the face of an unfettered Barcelona, particularly with one save from Villa, but the resistance could not continue. Barcelona quickly scored twice to assume the lead on aggregate. After 69 minutes, Iniesta and Villa combined in a perfect move, before Xavi put the ball past Almunia. Two minutes later, Koscielny fouled Pedro and Messi converted the penalty.
Arsenal, a man down, still sought a late goal that would then have redeemed them. They were on the verge of it when Jack Wilshere's excellent low ball from the right picked out the substitute Nicklas Bendtner but the Dane's poor touch allowed Javier Mascherano to intervene.
This campaign has hurt Arsenal on other occasions as well and Wenger will have not have forgotten the defeats in the group phase that led to their facing this daunting fixture.
Even so, the rise of the team is not to be scorned. There are still outlandish days, as when a 4-0 lead after 26 minutes was relinquished in the draw at Newcastle United. The side persevere and ought to have faith in their Premier League prospects.