Manager: Pep Guardiola
Star man: Lionel Messi
Best result: Four-time winners (1992, 2006, 2009, 2011)
Form so far: Devastating. Their record of five wins and a draw in the group stage was impressive anyway but that was before the 10-2 aggregate demolition of Bayer Leverkusen in the last 16.
The Spanish champions are close to averaging nearly four goals-a-game while they have conceded only six in the tournament all season.
Danger rating – 5/5: Hot favourites to become the first team to retain the trophy in the Champions League era.
Only AC Milan have been able to compete with them so far and that was only for about 45 minutes. They are the side that no one wants to draw but someone has to beat them eventually.
Manager: Roberto Di Matteo
Star man: Didier Drogba
Best result: Finalists (2008)
Form so far: It has not been vintage Chelsea in Europe this year. Only a win against Valencia on the last day of the group stage booked a last 16 place.
In the knock-out rounds they again looked on the brink of an exit against Napoli before a change of manager lifted spirits and secured the only quarter-final berth for a Premier League side.
Danger rating – 4/5: The old guard of Frank Lampard, John Terry and Didier Drogba have been criticised many times this season but their experience has been priceless at this level.
The defence looks shaky but the ever-reliable spine to the team means they are still a threat, especially at Stamford Bridge where they have scored 14 goals in four games.
Manager: Jupp Heynckes
Star man: Mario Gomez
Best result: Four-time winners (1974, 1975, 1976, 2001)
Form so far: Are you watching Manchester United? The German side did what Sir Alex Ferguson’s men couldn’t do and that was defeat Basle to send them packing in the last 16.
They made it look like a cakewalk too as their 7-0 victory at the Allianz Arena set the new record winning margin in a Champions League knock-out match.
Danger rating – 4/5: As Manchester City found out in the group stage this is not a side to be messed with.
It is one of the strongest the Bundesliga outfit have produced in recent years.
The key will be stopping striker Mario Gomez who has netted 10 times in seven games.
Manager: Jose Mourinho
Star man: Cristiano Ronaldo
Best result: Nine-time winners (1956, 1957, 1958, 1959, 1960, 1966, 1998, 2000, 2002)
Form so far: Conceding a late equaliser at CSKA Moscow in the last 16 has been their only slip-up in the entire tournament.
But even that was forgotten after a 4-1 win in the return leg at the Bernabeu and the competition’s record winners look more dangerous than ever under Mourinho.
Danger rating – 5/5: Barcelona are the bar in world football but Madrid are 10 points clear of them in La Liga and won every game in the Champions League group stage.
While no one will go as far as suggesting Barcelona’s dominance is coming to an end, it does show just how strong Madrid are this season.
Manager: Massimiliano Allegri
Star man: Zlatan Ibrahimovic
Best result: Seven-time winners (1963, 1969, 1989, 1990, 1994, 2003, 2007)
Form so far: In the Champions League they have been the Italian version of Chelsea – great going forward but a disaster at the back.
They were nearly victims of a shock comeback (even by their standards) after losing 3-0 at Arsenal in the last 16, but they just managed to edge through 4-3 on aggregate.
Danger rating – 3/5: The last time Milan reached the quarter-finals they won the tournament but it would be a shock if they were to lift the trophy for an eighth time.
The Serie A leaders are a good side but the ease in which Arsenal clawed back three first-half goals at the Emirates Stadium will only act to inspire other teams.
Manager: Jorge Jesus
Star man: Nicolas Gaitan
Best result: Two-time winners (1961, 1962)
Form so far: The Portuguese side have been involved since the third qualifying round back in July and have only lost one game.
But they made amends for the 3-2 defeat at Zenit in the last 16 by winning the second leg 2-0 at the Estadio da Luz to book their first quarter-final spot for six years.
Danger rating 3/5: Manchester United know about the threat they pose after being held to draws home and away in the group stage.
There is a strong team ethic and there is star quality too. Gaitan has been lethal in creating opportunities for likes of Oscar Cardozo this term.
Manager: Didier Deschamps
Star man: Loic Remy
Best result: Winners (1993)
Form so far: Procrastination has been a staple of their campaign. Two goals in the last five minutes at Borussia Dortmund just about saw them into the last 16 and it did not stop there.
Injury time strikes home and away sealed a 2-2 aggregate draw at Inter Milan where they progressed on away goals.
Danger rating – 2/5: Absolutely none…up until around 85 minutes.
Deschamps’ team have often played a cautious defensive game and only turn up the heat in the latter stages.
Fine against naive teams but better sides like Barcelona could be well out of sight before then.
Manager: Ivan Jovanovic
Star man: Nuno Morais
Best result: Quarter-finalists (2012)
Form so far: Amazing. When they took to the field in a second round qualifying match at Skenderbeu, nobody could have predicted they would be eliminating Lyon in the last 16 eight months later.
It may have been on penalties but the Cypriots topped their group previously – so they can play.
Danger rating – 1/5: Such is the shock they are still involved, APOEL would have snatched at a quarter-final place in the Europa League if you had offered them that at the start of the season.
They are the team everyone wants to face but the pressure is off the minnows.