In the 4-2-3-1 formation that has become so ubiquitous on the continent, there is usually a clear division in roles between the two central midfielders: one tasked with more defensive responsibilities, and the other pegged as the "passer", charged with distributing the ball into the attack.
At Dortmund, Ilkay Gündogan is firmly cast in the distributor role. Bought in the summer of 2011 from Nuremberg, he was a clear replacement for Nuri Sahin, who had departed for Real Madrid. After an easing-in period, where Klopp rotated between Sebastian Kehl, Sven Bender and Gündogan, the latter has become a first-choice player, helping Dortmund drive their attacks up the pitch. He could, theoretically, be used as the No. 10, but it is more likely he will be paired with Sven Bender, a mobile, energetic midfielder who regularly covers more than 12km a game.
Gündogan has gone under-the-radar, but a good performance against Madrid illustrated his talents: he was Dortmund's most prolific passer, helping connect the side, but he also surged forward to provide a physical presence in support of Mario Götze and Marco Reus. Klopp is highly appreciative of his talents, lauding him as "an extraordinary player ... he has turned into a real strategist."
Bayern's games against Juventus and Barcelona give a good indication of how they will deal with Gündogan. Mario Mandzukic and Thomas Muller are both extremely hard-working and took turns occupying Andrea Pirlo and Sergio Busquets (Mario Gomez also performed this role admirably in the first leg against Barcelona).
Their discipline and desire to get back help make Bayern compact, and with both Gündogan and Mats Hummels capable of picking out clever passes from deep positions, it will be important that the Bayern front two press from the front. In particular, Hummels brings an element of unpredictability to Dortmund's play, as he is able to bring the ball out from the back - which, conversely, can leave the defence exposed if he gives possession away cheaply.
Meanwhile, Munich's midfield pivot will be occupied by Javi Martinez and Bastian Schweinsteiger. Although they are lauded for their technical qualities, they are also very physical. No other team in Europe has completed more tackles per game, with the midfield duo looking to break up opposition counter-attacks with ruthless fouls.
Schweinsteiger will play on the left hand side of midfield, playing roughly the same role as his compatriot on the opposite side - dropping into deep, left-of-centre positions to either prompt counter-attacks or play a calmer, sideways pass to one of the attackers. Schweinsteiger is an excellent long-range passer, and with Bayern starting with two direct wingers, he will try and switch attacks quickly to the opposite flank to drag Dortmund out of shape.
Schweinsteiger and Gündogan -- both angling for the same position on the national team -- will both want to get on the ball and dictate the tempo. It is obvious that Klopp will go to great lengths to try and nullify Schweinsteiger's presence, having already enacted specific measures to counter Xabi Alonso's influence by instructing Götze to block off passing lanes to the Spaniard. Working in tandem with Robert Lewandowski, Dortmund's front two channeled Madrid's attacks away from Alonso.
"Our plan was to take Xabi out of the game, because if Alonso can play as he wants it is impossible to defend against Madrid," Klopp said earlier in the season. "If you block Xabi, you make it so Pepe always has the ball. That is a big difference."
This was so effective it prompted Jose Mourinho to re-jig his side for the second leg, with Khedira dropping to the bench and Luka Modric moving into a deeper role, and suddenly, Dortmund weren't sure how to nullify the presence of two deep-lying playmakers.
Dortmund might encounter a similar problem here, even if they manage to shut off passes to Schweinsteiger. Bayern have encountered this sort of tactical issue this season, where teams take specific measures to counter Schweinsteiger and leave Martinez free.
For example, in the DFK Pokal semi-final against Wolfsburg, Slobodan Medojevic was instructed to man-mark Schweinsteiger, so the German midfielder dragged him all the way across field towards the left touchline. Then, Javi Martinez pushed up-field, pushing Wolfsburg's midfield away from goal and opening up space for Daniel Van Buyten, who had the freedom to carry the ball forward and instigate passing moves.
It is a good example of Bayern's adaptability this season. Whereas the last four Champions League winners have won with an extreme brand of football - Barcelona with all-out possession, Chelsea and Inter with all-out defence - Bayern have the variety to switch between styles and adapt to specific tactical issues.
They have an organized, almost mechanical style of play. It is up to Klopp to spring a surprise.