Ever since sneaking into Hampden Park as a boy to watch Real Madrid's legendary 7-3 demolition of Eintracht Frankfurt in the European Cup final, Alex Ferguson has been acutely aware of the threat posed by the truly great Spanish sides.
Through his time in the hotseat with Aberdeen - sending shockwaves through Europe after upsetting Madrid to win the Cup Winners Cup in 1983 - to his days at Old Trafford - where he beat Johan Cruyff's Barcelona to win the same trophy eight years later - the Manchester United manager has forged a long-standing rivalry with the Spanish duo.
He's had his share of highs - beating Barca in the 2008 semi-final on the way to Ferguson's second Champions League success - as well as lows - the 4-0 demolition at Camp Nou in 1994 and quarter-final elimination against Real in 2000 in particular - but none are remembered as bitterly as the 2009 final loss to Barcelona in Rome.
Of course, Ferguson doesn't just hold grudges, he thrives on them - just ask Jaap Stam, Ruud van Nistelrooy or the BBC. Having had two whole years to let this one simmer, the Scotsman will be delighted to get another crack at a team many are already anointing as one of the best of all time, a title Ferguson will likely use to fire up his troops before sending them out on Saturday at Wembley Stadium, the site of breakthrough European Cup triumphs for both clubs.
There'll be no George Best or Ronald Koeman this time, of course, but Koeman's former teammate, Pep Guardiola, will be there, 19 years after teaming with the Dutchman to knock off Sampdoria under the now-demolished Twin Towers. Aiming for his second Champions League triumph as Barca manager in three years, Guardiola is sitting pretty, orchestrating the champagne football played by his all-star squad which delights both purists and partisans alike.
Ferguson will view the occasion as he always does, as a challenge, throwing down the gauntlet to his team to go out and earn the world's respect by knocking Barcelona off their perch, to borrow a phrase, and drawing on the experience gleaned two years ago in defeat.
There is a fear in Catalonia that United learned how to play with Barcelona that day, that the 2011 United vintage is a far more battle-hardened bunch than the likes of Cristiano Ronaldo and Carlos Tevez was two years ago.
And some of the current squad feel that Barcelona was lucky to catch United on an off day back then.
"None of our 11 players had a good feeling from that match," Red Devils goalkeeper Edwin van der Sar told the Observer last weekend. "It's never good when you lose but you can normally point to one or two who did their bit and had a decent game. I don't think there was a single United player from 2009 who could say he gave it everything and played well."
With the Dutchman about to play his last game before hanging up his boots for good, giving his all should be a given this time around, although there was little he could do to prevent Samuel Eto'o and Lionel Messi from scoring the goals in '09.
Ferguson won't accept anything less than the best from his players this time either, just as he has done since the day he took over the club in 1985, and did most famously at half-time of the 1999 Champions League final, trailing 1-0 to Bayern Munich.
"At the end of this game, the European Cup will be only six feet away from you and you'll not even be able to touch it if we lose. And for many of you that will be the closest you will ever get. Don't you dare come back in here without giving your all."
That speech may have passed into Old Trafford folklore, but for Ferguson, aiming for his third European Cup triumph to tie the record held by legendary Liverpool boss Bob Paisley, the same determination to succeed is very much in the here and now.
David Villa v. Fabio Da Silva
Both Fabio and his twin brother Rafael are in the running to play right-back for United on Saturday, but whoever wins is guaranteed of an uncomfortable day at the office. Fabio's disciplinary record means he's favoured to start - Rafael's dismissal in last year's quarter-final against Bayern Munich did much to contribute to United elimination that day - but with only eight Champions League appearances under his belt, a speedy World Cup winner like Villa - Spain's record international goal scorer - will certainly fancy his chances.
Javier Hernandez v. Javier Mascherano
There's no guarantee that Ferguson will plump for Hernandez, or Chicharito as he's better known these days, but whenever he gets on the pitch, the Mexican wunderkind can wreak havoc with the makeshift Barcelona defence. Central defence stalwart Carles Puyol is likely to remain at left back, leaving former Liverpool midfielder Mascherano to slide back to take his place. But the big question mark is going to be how he deals with the pace and goal-scoring ability of United's rookie.
Lionel Messi v. Rio Ferdinand/Nemanja Vidic
Playing as a fake No. 9, the Argentine superstar is going to pose a massive threat to United's chances of success. His ability to draw the central defenders out of position with his incisive running was a massive part of Barca's semi-final victory over Real Madrid, and it will require discipline, awareness and a certain amount of luck if United's centre-backs are to avoid the same fate at Wembley on Saturday.
United sitting pretty
You have to go all the way back to 1927 to find the last time a non-English team won a meaningful final at Wembley, when Cardiff City beat Arsenal in the FA Cup final. Since then Benfica, Brugge, 1860 Munich and Cardiff again have all failed to beat domestic opposition at the home of English football.
United sitting pretty II
Only three times in the history of the European Cup/Champions League has a team lost a final in its own country, while six have won. Reims, Roma and Barcelona were the unlucky trio, while Real Madrid, Internazionale, Manchester United, Ajax, Liverpool and Juventus proved successful.
Barcelona is the favourite in this year's final, but if United wanted to draw on something positive it can look to the Argentine's scoring record in England. Despite scoring 52 goals in all competitions this season, the world player of the year has yet to find the back of an English net, drawing blanks in six contests over the past five seasons against Arsenal, Chelsea, Liverpool and United. The Red Devils will likely be pinning their hopes on making it seven.