The front three players for both Clasico sides generally get the brunt of the attention for better or worse, and often rightly so as they are the two best attacking fronts in the world by some distance. However, it's the three men behind them that generally set the tone and provide the service for the BBC and MSN to wreak havoc on defenses. Let's take a look at the probable midfield selections.
Projected starters: Luka Modric, Toni Kroos, Isco Alarcon
Real Madrid comes into this game with Kroos sitting second in the league in pass completion rate while he and Isco have 15 league assists between them, the best assisting combination in the league. If James Rodriguez were healthy enough to play Madrid's midfield would be by far the more prolific assisting side. It's not as if Barcelona's midfield is short of creativity and assists, but it's moreso that Madrid relies more on its midfield for shot generation so it's of the utmost importance that the trio makes the most of what should be, limited possession.
Kroos will likely be the deepest of the three. He's averaging a healthy 2.5 tackles per game which, for someone who is not a natural defensive midfielder, is fairly impressive. Kroos, as previously mentioned, is second in the league with a whopping 92.3 percent pass completion rate and given that Madrid's strategy will surely to try and hit Barca on the counter, Kroos' specialty of accurate longballs will have to be on point to let the BBC loose.
To his right will be Luka Modric, fresh off of two cameo apprentices following a four month layoff. When healthy there's no doubt that Modric is a bona fide top-3 midfielder in the world with his ability to win the ball and dictate play through various tempos. However, he did just return from a significant time off and asking him to chase around the likes of Lionel Messi for 90 minutes will be a tall task. Madrid will likely want less defense and more transitional play once the ball is won from Barcelona. However, even though he likely won't be playing at 100 percent his presence will be an enormous boost to Gareth Bale as the Welshman plays noticeably better with Modric supporting him.
Arguably the big wildcard will be Isco Alarcon on the left. Though Isco played a massive role in the 3-1 victory over Barcelona in the first meeting as he pick-pocketed Andres Iniesta, he will be the youngest and least experienced midfielder starting on Sunday. His dribbling and close control skills will be imperative against a side looking to press and quickly win the ball back. He'll also have to cover the gaps Marcelo leaves behind as he surges forward since Luis Suarez and Messi will be looking to exploit these spaces.
Defensively, we can probably expect Bale to drop back while Modric tucks in to form a midfield four and a second bank in front of the defense. The key will be to be disciplined and to anticipate the opposing midfielders sliding into gaps when Suarez and Neymar make their runs to draw away defenders. Pressing Barcelona hard wouldn't be advised as their passing is so quick that it more often than not evades the press.
Projected starters: Andres Iniesta, Ivan Rakitic, Javier Mascherano
With Sergio Busquets' injury, it was natural for some Barcelona fans to panic while the Madrid contingent celebrated, but perhaps it should be the opposite happening. Busquets is a fine footballer, there is no doubt of that, but it is Mascherano which is the more "pure" defensive midfielder who shields the back four while springing counter-attacks through the longball. He's not as possession-happy as Busquets is, but he does provide more pace and power and though he does play the riskier pass on occasion, it can also lead to the home run ball the MSN has begun to thrive off of. This will hardly be a dropoff from Busquets at all.
Rakitic, after some growing pains, is truly starting to find his stride in this offense both from a defensive and passing perspective as well as a goal contributing one. With four goals and six assists in the league as well as being a free kick specialist, he gives Barcelona an added threat to score from further back. He doesn't have the defensive nous of Mascherano but he certainly provides the work ethic and tenacity to try and win the ball back when not in possession and will provide Iniesta the ability to attack more knowing that he has additional cover behind him.
Iniesta is the most veteran midfielder who'll be starting. Whether that benefits Barcelona or leaves them exposed is to be seen. While he's nowhere near the imperious form of the Pep Guardiola era, his calm under fire and telepathic connection with Messi will surely be boosted under home lights. The onus to create opportunities will likely be less on him with likely more of a role to take care of the ball and to find Messi. Madrid doesn't need their midfield to aggressively press Barcelona's, but if there's one individual they can key on given his age and declining pace it's Iniesta. We saw this in the first meeting.
Real Madrid: Lucas Silva, Asier Illarramendi
Barcelona: Xavi, Rafinha
Real Madrid holds the edge in holding midfielders should they be clutching on to a lead late while Barcelona has veteran experience and the dynamic Rafinha should they need to introduce another weapon. Based on what the bench players can bring to the table, Madrid has a defensive midfielder and someone who can venture forward in attack while Barca's defensive cover is dangerously thin should Mascherano have to leave the game. That being said, no one should count out Xavi's experience.
Advantage in midfield
Both midfields are world class and likely top-3 overall. Barcelona possesses the best defensive midfielder of the bunch while Madrid's is more dynamic and offensively dangerous. If Luka Modric can regain (and this is a lot to ask) his form of a few months ago and if Kroos is truly rested for this game, then the very slight edge might go to Madrid due to their youth and capability to contribute on both ends. However, this is a coin flip and one can make a very strong case for Barcelona as well. This is where the game could very well be won.