Cristiano Ronaldo
Cristiano Ronaldo's ability to hit the ground running after his return to fitness will be crucial to Real Madrid's chances against Bayern Munich. Reuters

Two of Europe’s most successful clubs meet on Wednesday in the first leg of a Champions League semifinal that will have all the feel of a final itself.

Current holders and five-time European champions Bayern Munich will travel to a Real Madrid side still chasing a 10th continental crown. It will be a rematch of the semifinal of 2012 when Bayern were victorious on penalties, but both sides have changed considerably since then.

Here’s how they’ll match up at the Bernabeu.

Goalkeepers
Manuel Neuer may make the very occasional error, but few will argue with his selection in FIFA’s World XI earlier this year. His opposite number will be another of the world’s top goalkeepers. Iker Casillas may have not played a league fixture for well over a year now, but he showed he remains s remarkable shot stopper to help Real Madrid just about hold off a second-leg fight back from Borussia Dortmund in the quarterfinals. The reason that both Jose Mourinho and Carlo Ancelotti have overlooked him for Diego Lopez in the league, though, is that he can sometimes lack command over his area.

Defenses
There can be little question that the weakest part of both teams is their defense. Madrid may have become a team who now control the ball more under Ancelotti, but they will surely be looking to replicate what they did so well under Mourinho and hit Bayern hard and fast on the counter attack. The pace of Cristiano Ronaldo, Gareth Bale and Angel di Maria could do much damage to Bayern’s center-back duo -- likely Dante and Jerome Boateng -- who are often left isolated. They showed their vulnerability early on in the first leg of their last-16 clash with Arsenal when they were attacked with pace. To help counter the threat, Philipp Lahm will likely return to right-back, where he dealt so well with Ronaldo in both legs of 2012’s semifinal.

Madrid’s duo can also be a source of optimism for the opposition. Both Pepe and Sergio Ramos can look supreme defenders at times, however they all too often make poor, rash decisions. The fact that the full-backs either side of them like to go forward so much means they aren’t offered a lot of protection.

Midfields
Madrid’s defense also receives little protection from their midfield. The greatest shift under Ancelotti has been toward a midfield more focused on what they can do with rather than without the ball. Luka Modric, who featured little under Mourinho, has a strong argument to be Madrid’s player of the season, with his passing acumen and ability to run through the lines a feature of the team’s play. Di Maria uses his energy and pace well on the left. In the middle Xabi Alonso is still a fine passer of the ball, but his lack of physicality and mobility make him a less than ideal candidate to be the most defensively minded midfielder.

While they will again be missing Thiago Alcantara, Bayern have the best collection of midfielders in Europe and a better balance than Madrid. Bastian Schweinsteiger and/or Javi Martinez can provide the physicality as well as ability on the ball as they did so memorably in the destruction of Barcelona at the same stage of the Champions League last season. More forward thinking, Toni Kroos embodies the idea of the modern midfielder. Kroos can play either deep, centrally or advanced and combines every aspect of required for those roles. That trio might well be deployed to provide solidity away from home, although Pep Guardiola also has more attacking options in the effective Thomas Muller and talented Mario Gotze.

Forwards
At their best, Madrid’s BBC forward line is unmatched across Europe. There are doubts coming into the match, though, over Ronaldo, who will make his return after three weeks out, as well as Bale, who couldn’t train on Monday as he battled the flu. The pair will be key to Madrid’s hopes of catching Madrid on the break, while Karim Benzema has been a more assured presence in front of goal this season.

For Bayern, Franck Ribery is a more technical winger and the explosive, but often frustrating, Arjen Robben will be looking to exploit the attacking instincts of the fit again Marcelo. One of Guardiola’s biggest selection dilemmas is who he starts up front. Away from home in Bayern’s quarterfinal against Manchester United, Muller started but it left the side without the type of presence up front that Mario Mandzukic can provide. Yet, Madrid are sure to enjoy more possession that Manchester United did, perhaps seeing Guardiola lean toward the extra controlling presence offered by Muller, or even Gotze in a false-nine role.

It’s hard to imagine there not being goals with both sides wanting to play on the front foot. But the greater ability of Bayern to control the ball, coupled with doubts about the fitness of Ronaldo and Bale should allow Bayern to emerge with at least a draw to make them favorites for the return leg.

Prediction: Real Madrid 1-1 Bayern Munich