Former Schalke 04 playmaker Ivan Rakitic is playing as a central midfielder for Unai Emery. That created a lot of controversy in Sevilla, but the Croatian player is performing brilliantly and he's Sevilla's leading scorer so far. The Andalusian team signed Marko Marin on loan from Chelsea and the small winger is showing why he was a great prospect during his time with Werder Bremen.
Those two are Sevilla's most dangerous weapons, although strikers Kevin Gameiro and Carlos Bacca are currently fighting for a starting spot and therefore, both of them are playing hard. Gameiro is a fine striker for Sevilla, even though he didn't have a lot of playing time under Carlo Ancelotti during PSG's 2012-2013 season. The French striker could be seeking revenge and he will likely be Sevilla's starter against Real Madrid.
Unai Emery is a creative coach whose plans usually surprise the opposition's coach. For example, he had the idea of playing with Mathieu and Jordi Alba when he was Valencia's manager, and that used to cause Pep Guardiola's Barcelona some trouble.
But if he sticks to plan against Real Madrid, Sevilla will play with their classic 4-2-3-1 formation. Stéphane Mbia is the one midfielder in charge of stopping the opposition's playmakers. He's a very physical player, but he doesn't have the quality needed to control the tempo of the game. Emery knows that and that's why Rakitic's position is vital for him. As stated above, Rakitic was never a central midfielder, so he doesn't have a great work-rate. But he does have the quality and pace to be a good central midfielder if he has a player like Mbia saving his back.
Vitolo, Jairo and Perotti will play behind the striker, because Marin will miss the match with an injury. Vitolo is not a steady player, but he's a creative attacker who could harm Real Madrid's defense. Perotti's pace should also worry Marcelo, because Real Madrid's left back is not used to track back, so he will need Ramos or Pepe's protection. Illarramendi's positioning should also be key against these three attackers.
Sevilla's offensive line is vulnerable. Nico Pareja, Coke, Carriço and Alberto Moreno aren't great defenders. Moreno was rumored to be a Real Madrid-target, and he's certainly a good prospect, but he should struggle against Real Madrid's right wing. If Real Madrid play well enough, Sevilla's defenders will not have an easy time at the Bernabéu.
Portuguese goalkeeper Beto took over Sevilla's goal after the Andalusian team sold Palop and Diego López last season. He showed his skills during the second half of the season, but he's not a brilliant goalkeeper neither.
All things considered, Sevilla have a good roster and a good coach, and that's why they're currently ranked 10th in the Liga BBVA after such a difficult start. But they probably don't have the quality to stop Real Madrid at the Santiago Bernabéu.