The old cliche goes that in knockout football any team can beat any other.

While the bookies might not agree as far as APOEL Nicosia are concerned, the Cypriot side are in the last eight as many far bigger European clubs have fallen by the wayside.

The Spanish duo of Barcelona and Real Madrid are clearly the teams to beat, but here are one big reason why each of the quarterfinalists can hold out hope of lifting the trophy in Munich.

APOEL Nicosia: Luck

APOEL's run to the quarterfinals of the Champions League has been little short of remarkable. 

Their began campaign in the qualifying rounds in July began against Albanian side Skënderbeu Korçë, and continued with them topping a group which included Europa League champions Porto and Champions League regulars Shakhtar Donetsk and Zenit St Petersburg.

Their heart-stopping penalty shootout win over Lyon was just another chapter in what has been a compelling story, but they will face their toughest test imaginable against Real Madrid in the next round.

With their team of journeymen taking on Real's expensive collection of superstars—and the winner probably facing Barcelona—APOEL will need more than a hefty slice of good fortune if they are to achieve the impossible.

Marseille: Deschamps

Marseille can count themselves fortunate to be in the quarterfinals at all. In all likelihood, it was only a kind draw against an Inter Milan side at a low ebb which saw them through the last 16, and even then it took a late winner in the second leg for them to do so.

However, in coach Didier Deschamps they have a man at the helm who has seen it all. As a player he won multiple league titles in different countries as well as the Champions League, not to mention the World Cup and European Championships with France.

The diminutive midfielder also led Monaco to the Champions League final as their manager in 2004, only for the principality club to be beaten by Jose Mourinho's Porto.

Such experience in the dugout may be the biggest asset Marseille have in their locker when they face off against Bayern Munich in the last eight.

Benfica: Craft

Benfica's feat of securing two score draws against Manchester United in the group stage has since been proven not to be the most remarkable achievement, considering how the Red Devils fared in their other European fixtures this season.

Nevertheless, those results were a fine showcase for the abundance of creative talent in the Lisbon club's squad.

With the likes of Bruno Cesar, Axel Witsel, Nicolas Gaitan and veteran playmaker Pablo Aimar, the Eagles can boast at least as much attacking guile as any other side in Europe.

Chelsea: Autonomy

Andre Villas-Boas was poached from his job as manager of Porto at great expense in order to oversee a gradual phasing out of the club's ageing stars and an introduction of young talent to take their place.

As you are no doubt aware, it didn't work out. The Portuguese coach was sacked and in came Roberto Di Matteo on an interim basis.

Just as when they reached the Champions League final in 2008 with Avram Grant as caretaker manager, Chelsea's players are once more thriving by virtually coaching themselves. Witness John Terry's domineering press conference appearance and his barking from the dugout after being substituted during the thrilling win over Napoli which saw them through to the quarterfinals.

Whatever is happening at Chelsea these days it appears to be working. Wednesday night's defeat at Manchester City was their first in five matches under Di Matteo. Left tot heir own devices, could Chelsea's old guard see them through to the Munich final?

AC Milan: Champions

AC Milan are the only club that can hold a candle to either Real Madrid's all-time record of nine European Cup triumphs or Barcelona's run of three trophies in the last decade.

The Rossoneri are the next most successful club in the history of the competition, lifting the trophy seven times—twice in the last 10 years—and also reaching another final.

As such it would be foolhardy to completely rule out the Italian giants—who look set to retain their Serie A title this season—especially as they finally broke their recent habit of losing to English opponents in the last 16. 

Bayern Munich: Robbery

Bayern Munich's season has been a frustratingly inconsistent one, with sublime results followed by the ridiculous.

At the time of writing, the Bavarian giants are enjoying a run of the former, having scored 20 goals in their last four games, the most recent of those a 0-0 draw in the German Cup.

While a great deal of credit for that must go to goal machine Mario Gomez, it is the coincidental returns to form of both Arjen Robben and Franck Ribery that have sparked Jupp Heynckes's team to life at such a crucial stage of the season.

Real Madrid: Arrogance

While displays of arrogance, for the most part, are rightly frowned upon in polite society, there is always a place for it at the elite level of any sport.

Few clubs embody the characteristic quite like Real Madrid. It is a sign of their great conceit that they have just announced the construction of a $1 billion Real Madrid resort in the Middle East, for example.

But Los Merengues have earned the right to look down their noses. After all, they have won the European Cup an incredible nine times, including the first five instalments in the 1950s. 

Their current manager, Jose Mourinho, has built his whole psychological approach around imbuing his players with supreme self-belief, and he ha the medals to prove it works. 

Their star player, Cristiano Ronaldo, is arrogance personified, but one look at his goal tally and status as the world's most expensive footballer tells you why.

In the latter stages of a competition,  an internal crisis in confidence can be more dangerous than any opponent on the field.

In the Real Madrid camp, there is no room for doubt. They believe that this season they are the best, and are just waiting for the chance to show it.

Barcelona: Messi

There is, of course, a plethora of world class talent on Barcelona's books. It was only last year when the three-man shortlist for the Ballon d'Or was made up exclusively of players who call the Nou Camp home.

But right now, perhaps more than any other time in his career, belongs to the club's No.10, Lionel Messi.

The Argentina forward broke the club's all-time goal-scoring record on Tuesday night with a hat-trick against Granada, passing Cesar Rodriguez's 60-year-old mark with an exquisite chip over the keeper. 

Even by his own absurdly high standards, his current run of 17 goals in his last seven games is truly mind-blowing. If he continues in such a vein of form until the end of the season, it's hard to see how Barca won't retain the trophy.