Barcelona'sworst fears were confirmed, but so were Arsenal's – Pep Guardiola's second-string centre-halves made a nervous start, but an awesome Leo Messi had the game wrapped up by half-time.
Only Barça's genial No 10 and midfield maestro Xavi were at their best in the first half but that was more than enough against an Arsenal side unable to take advantage of the weaknesses in the hosts' rearguard.
In the absence of Gerard Pique and Carles Puyol, Guardiola was forced to pair two defenders who had not played alongside each other in such an important match since the 2008 Champions League semi-final against Manchester United, and it showed. Gabi Milito and Rafa Marquez were like strangers in the night and there were 12 minutes on the clock before Milito played a pass out of defence that did not go to a white shirt.
The Argentine injured cruciate ligaments in his right knee in that game against United and missed a year and a half of football. He had started five of Barcelona's last nine games before last night.
His central defensive partner Marquez had played just 17 minutes in that time and the pair were torn apart when Milito lost out to Abou Diaby in midfield and Theo Walcott raced clear to set up Nicklas Bendtner for the opening goal.
Not only did Barça look shaky going backwards, they looked positively sidewards coming forward.
Arsène Wenger spoke of an opportunity lost when he said afterwards: "I think we had the chance to score the second goal but Messi is a player who can take advantage of your mistakes at any moment. If we had taken every chance then we would have done it. Before they levelled we had a great chance to score again but we made a bad decision with the final ball."
Almunia was a spectator early on as four of Milito's first five passes went astray and the careless distribution was contagious with the usually comfortable Eric Abidal losing possession at every opportunity.
But it mattered not because at the other end of the pitch was the world's greatest footballer. Messi's 21-minute hat-trick woke his team up and knocked Arsenal clean out, the striker adding a fourth in the second half. He now has 39 goals in all competitions.
The debate over whether Messi is as good as Diego Maradona hangs on the few things that Maradona did that Messi is unable to do – lead his team being the most obvious.
Messi is as shy as Maradona was brash and he has never looked Barcelona captain material, until last night. Barcelona supporters were nervous in the lead-up to the game and those first 15 minutes did nothing to ease the nerves, but Messi answered the call and his brilliance covered a multitude of defensive sins.
Guardiola had, as expected, left Thierry Henry out of his starting line-up choosing 19-year-old Bojan Krkic instead but the Catalan youngster made a nervous start and was unable to take advantage of an Arsenal side missing Alexander Song, William Gallas and Sol Campbell.
Young Canary Islands winger Pedro was also out of sorts playing the biggest game of his career so far.
Pedro had Xavi shouting in his ear in that nervous first half as the captain fought a lone battle in midfield for the home side. Alongside him was Sergio Busquets, another Barça youngster freezing on the big night.
Seydou Keita, the third man in Barça's midfield trio, was also below par and with Abidal having his worst 45 minutes of the season, Barça looked a shadow of the side that has been so dominant at the Nou Camp.
Xavi's contribution should not be underestimated. The fulcrum of Barcelona's triumphant charge to the trophy last season has missed his partner-in-crime, Andres Iniesta, in recent weeks. The pair have a telepathic understanding but Iniesta started on the bench. Xavi was carrying an extra weight but with Messi in support he did not buckle.
Xavi and Messi saved not only their team-mates but the coach who looked to have got his team selection wrong after Arsenal's goal went in. The decision to leave out Yaya Touré had robbed Barcelona of a player who would have been capable of coming out from the back with the ball. Guardiola finally brought on Touré after half-time and took off the ineffective Bojan but by then the result was all but decided. Messi had lifted everyone... even Milito and Marquez.