Barcelona taught global football spectators a rather obvious lesson this week: Don't write us off. Ever.

Week-in and week-out, the Spanish giants deploy arguably the greatest team ever assembled in club football. And yet, following a two-goal loss in the first leg of its Champions League tie with AC Milan a fortnight ago, some had the gall to suggest that Barcelona's number had been called in this year's competition.

Any suspicion of the Catalans exiting the tournament was wiped away within the opening five minutes of the return leg on Tuesday as Lionel Messi cut the aggregate deficit in half with an exceptional (even by his standards) curling strike into the upper corner.

Barcelona's progression was under threat for all of 10 seconds when M'baye Niang struck the woodwork on a breakaway in the 38th minute, but the Camp Nou enjoyed a collective sigh of relief a minute later when Messi grabbed his second of the match. David Villa and Jordi Alba produced the second-half goals to see the La Liga club through to the quarterfinals.

Doubters could not be blamed for writing Barcelona off before Tuesday's clash. After all, the club entered the match enduring a poor run of form with three losses from its last four across all competitions. Was it the absence of manager Tito Vilanova, a lack of a proper response to temporary boss Jordi Roura, or simply a complacency stemming from a substantial lead in the La Liga table finally setting in? All of those issues may have been intertwined, but there was no denying that the Barcelona of recent weeks was not the same Barcelona we had seen for the first six-plus months of the season.

And despite the adversity, Roura's side managed to prove the skeptics wrong, turning out a vintage performance that saw Barcelona enjoy about two-thirds of the possession. It was a dominant display that serves as a reminder that Barcelona's best is superior to anything the seven remaining clubs have to offer.

That said, should Barcelona suffer a catastrophic injury to you-know-who or should the Catalans simply fail to show up in the face of elimination, there are two clubs that have what it takes to hoist the European Cup.

Bayern Munich proved to be the anti-Barcelona in its Round of 16 tie with Arsenal, cruising to a comfortable victory in England in the opening leg before falling at home to the Gunners this week. The Bavarians advanced on away goals, but it was an unconvincing output that had many questioning their credentials. Such cynics can be grouped together with those who dismissed Barcelona's chances of getting past Milan.

Top-to-bottom, Bayern has arguably the strongest squad in the world, and last season's disappointment in the final against Chelsea will motivate the Bundesliga leaders to take it a step further this go-around. They have been paired with Juventus in a quarterfinal tie that is sure to be closely contested, but Bayern should manage to progress.

Real Madrid, meanwhile, has proven its title mettle by dispatching Manchester United in the Round of 16, eliminating one more heavyweight from contention. Jose Mourinho has gotten the better of Roura this season as Madrid has posted a 2-0-2 against Barca in all competitions this term.

But in order to have a chance to knock off the Catalans, the Merengues first must find a way past Galatasaray, one of the sleepers of the tournament. No team enjoys traveling to the hostile land of the Turks, but the talent gap between the two sides weighs heavily in favor of Madrid.

With Barcelona drawn against PSG, the stars certainly appear to be aligned for the three-biggest European heavyweights to make it through to the semifinals where they will be joined by the winner of the Borussia Dortmund-Malaga tie.

The field seems wide open as the juggernauts avoided each other in the quarterfinal draw, but Barcelona showed this week why it is the clear favorite.

Perhaps the only ones crazy enough to bet against the Catalans will be their opponents.