In the entire history of the European Cup, I can find only four teams who have done what Barcelona must do next week: overturn a two-goal deficit from the first leg of a semi-final.
The first club to do so, bizarrely, was Inter, who lost 3-1 at Anfield in 1965 to Bill ShanklyâÂÂs Liverpool and won 3-0 at the San Siro, reaching the final â as any Red will tell you â partly because Inter had a little help from the referee.
The last team to stage this kind of comeback, spookier still, were Barcelona who, in 1986, got stuffed 3-0 by IFK Gothenburg in Sweden, won the second leg by the same score at the Camp Nou and prevailed in the penalty shootout.
After donning a metaphorical anorak and trawling through the archives, my research suggests that 22 clubs have tried to do what Barcelona need to do at this stage in the competition.
Eighteen failed â few more agonisingly than PSV who, in 2005, were within minutes of knocking out Milan before Massimo AmbrosiniâÂÂs late away goal.
Heurelho Gomes and Alex were among the beaten PSV players in 2005
Guus Hiddink, with the self-confidence that only comes from being worshipped as a virtual deity in such disparate parts of the world as Korea, Eindhoven and Stamford Bridge, still insists that his side would have beaten Liverpool in Istanbul.
The other two teams to successfully come back from the brink are Hamburg (who lost 2-0 to Real Madrid in the Bernabeu in 1980 but thrashed Los Blancos 5-1 in the return) and Roma, who broke Dundee UnitedâÂÂs hearts in 1984.
Inter, as you may have noticed, are the only team to stage such a comeback and then win the final.
What does all this mean? Not much except, perhaps, that Jose Mourinho has reached the tipping point in his career at Inter.
Calcio may all bow down to the tactical genius of âÂÂMouâ this week but come next Thursday, if Barca run amok on their own turf as Hamburg did in 1980, he could be dodging tomatoes.
Inter have done half the job but should heed the wise words of the great Mario Kempes: âÂÂTwo-nil is the most dangerous score in football."
(In the same interview, for Champions, he also said: âÂÂNever rub the head of a bald Indonesianâ but thatâÂÂs for another blog).
LyonâÂÂs mission is more straightforward. Claude Puel wonâÂÂt let them play that poorly again. Their 534-mile coach trip to Munich didnâÂÂt help.
Hugo Lloris looks back in anger as Bayern take a first leg lead
I know, I know, old timers will insist that in their day footballers could run that distance to that game and still score a hat-trick before quaffing 15 pints after the game but times, if not attitudes, have changed.
The differences between winners and losers are now so small that such travails â apart from anything the sheer boredom must be enervating â can decide a tie.
In Munich, Les Gones played as if they were suffering from a kind of footballing altitude sickness, as if awed by the realisation that they had come this far for the first time.
In front of their own fans, knowing precisely what they have to do, they should be much more focused.
If they can put serious pressure on BayernâÂÂs young defenders Diego Contento (who is 19) and Holger Badstuber (21) and make the most of Philip LahmâÂÂs slight dip in form, they could yet reach their first UEFA Champions League final.
Bayern have shown great resilience since they overwhelmed Juventus in Turin. They are now the only team to win four Champions League knockout ties and they have the look of a team with luck on their side.
But their margins of victory have been thinner than a size zero model. They have lost their last two away games in the competition but still progressed.
"Who you calling flat-faced?"
ItâÂÂs nice to see Louis van Gaal back at the top. As Simon Kuper has noted, he is ungainly, pot-bellied and flat-faced but has âÂÂone saving grace, he is brilliant.âÂÂ
KuperâÂÂs suggestion that Van Gaal is âÂÂthat rare manager who constantly improves his teamsâ performancesâ may surprise fans of Barcelona and Holland who failed to reach the 2002 World Cup finals under his tutelage.
He left the national side insisting: âÂÂSome of the players refused to accept my methods. I am who I am. IâÂÂm not going to change that and I have no desire to.âÂÂ
But his enraged schoolmaster shtick has worked brilliantly at Ajax (where he won the UEFA Cup, a trophy that saved his job, as well as the Champions League), AZ and now Bayern.
Hard to believe that before Christmas the manager with a Michael Portillo quiff was only six games from the sack.
The worry for Bayern must be that as long ago as 2000 Van Gaal talked of himself as a potential successor to Sir Alex Ferguson.
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