For the second night in a row, Spain takes on Germany in the Champions League, and as was the case in Barcelona verus Bayern, these two sides are remarkably similar. Both play a 4-2-3-1 formation based on transitions, focus their attack down the left hand side, and for both of them, this represents their final chance to win a trophy this season.
Jose Mourinho is keenly aware of the threat posed by Dortmund, having already drawn and lost to the German side in the group stage. "If they go through," he said at the time, "they are candidates to win the tournament."
Real Madrid's starting team is seemingly obvious to predict after Jose Mourinho took the unusual step of naming his starting XI in Tuesday's pre-match press conference. "Diego Lopez, Sergio Ramos, (Raphael) Varane, Pepe, (Fabio) Coentrao, (Sami) Khedira, Xabi Alonso, Mesut (Ozil), Higuain, Cristiano (Ronaldo) and hopefully Di Maria," says Mourinho, but given his history of subterfuge, this could be an elaborate ploy to disguise a last-minute tactical switch. Madrid have experimented in recent weeks with a 4-3-3 formation, so this cannot be ruled out - but straying away from the ‘settled' big game side seems unlikely.
Meanwhile, Klopp's major headache this week has concerned Mario Götze's impending move to Bayern Munich, which has disrupted his preparations for this clash. "It could have been timed better," Klopp told a press conference this week, but the news shouldn't change the starting line-up. Götze will be used in the centre of the attacking trio of Marco Reus and Jakub Blaszczykowski, while it seems likely that Klopp will use the same midfield duo of Ilkay Gundogan and Sebastian Kehl that featured in the last clash between these two sides.
The tempo of this game will be very important. In a clash between two sides playing broadly on the counter-attack, there are broadly two possibilities: the game becomes extremely open and centred around transitions, with players streaming forward every time they win the ball, or the game becomes stagnated, with neither side willing to take the initiative for fear of being caught out on the break.
The key for either side is the influence their ‘passing' midfielder has on the game. For the home side, that is İlkay Gündoğan, who can launch quick breaks with a broad range of passing, but is also capable of bursting forward to support attacks with his sheer energy. With Mesut Ozil not disciplined enough to be deigned to a man-marking job, Mourinho will ask Sami Khedira to track Gündoğan in open play. The two compatriots are relatively similar players and it will be interesting to see which of them can assert their physicality on the game.
Meanwhile, Real Madrid's ‘trigger' - the player that prompts their rapid counter-attacks - is undoubtedly Xabi Alonso. Klopp is keenly aware of this, and discussed how he set up his side to nullify the Spaniard during the group stage matches.
"We knew where they send their passes, how they look for Cristiano," Klopp said. "Our plan was to take Xabi Alonso out of the game. Because if Alonso is allowed to play how he wants it's impossible to defend against Madrid. And Götze covered him. We knew that if our wide players, Piszczek and Schmelzer move a lot, the advantage was ours on Cristiano's side of the pitch. If you block Xabi, you oblige Pepe to always keep the ball."
The use of Götze as a defensive shield was key - the young playmaker dropped onto Alonso when his side lost the ball, and forced him into extremely deep positions, almost as a central defender. The closer he was pushed towards his own goal, the more difficult it is for Alonso to complete his usually precise diagonals, as was obvious when Danny Welbeck man-marked him for Manchester United in the quarter final. If Götze does a similar job here, Raphael Varane will try to advance into midfield to hit long passes towards Ronaldo, but that might prove difficult. This is where Mourinho's 4-3-3 experimentations has rationality: it opens up a position in midfield for Luka Modric, who is certainly capable of hitting through balls into the path of Ronaldo - even if the Croatian doesn't start, expect him to feature at some point.
The logic is stop Alonso, stop Cristiano Ronaldo, and whilst it's true that the Portuguese winger is dependent on the service provided by Alonso's diagonal passes, he is also capable of creating his own service through powerful runs from the left flank onto goal, meaning Lukas Piszczek will stick tight to his man and allow himself to be dragged inside.
It is from his flank that Real attack most frequently, owing much to the intelligence of Mesut Ozil, who drifts wide from his central playmaker position to open up space for Ronaldo to cut inside - a ploy that devastatingly effective in Real's quarter-final tie with Galatasaray.
With Götze tracking Alonso and Gündoğan and Khedira set to do battle, the duty of tracking Ozil and keeping tabs on Ronaldo's darts inside will fall to the ‘second' midfielder in Dortmund's double pivot - either Sven Bender or Sebastian Kehl. The latter did not play on Saturday against Mainz and so appears likely to start here, and will have his hands full with Ozil's constant floating to either flank. This is not a man-marking job but a zonal responsibility, and whoever plays must not be dragged wildly out of position by Ozil's intelligent movement. They also have a secondary function: to act as a blocker in the inside-right channel, restricting the space in and around the edge of the penalty area for Ronaldo to cut into. Klopp will have studied Madrid's tie against Manchester United, and noted how effective Phil Jones was at performing this role.
Ronaldo's potential impact upon this contest is emboldened by the fact that Gonzalo Higuain will start up front, rather than Karim Benzema. The Argentine does not always bring his goal-scoring touch but is clever with his movements, timing his runs from the left hand side of the pitch in an effort to drag right-sided centre-backs out of position.
Of course, on the flipside of every strength therein lies a weakness, and Madrid's is obvious - the space exposed by Ronaldo's high positioning. This was particularly problematic in Madrid's group stage loss to those opponents, and will certainly be a factor here, given Dortmund too like to focus their attack down their left hand side. It was the right - Madrid's left - they targeted earlier this season, with Mario Götze and Marco Reus combining for quick one-twos in between the lines to magical effect, with Kevin Großkreutz providing balance on the left flank.
It will probably be the ‘normal' side here, with Jakub Blaszczykowski fit to start on the right, meaning Reus will dart inside from the left hand channel. That will be a stern test for Madrid's left-back, likely to be Fabio Coentrao, provided he is fit to start. That niggling doubt over his availability will be a source of great encouragement for Klopp, especially with Ronaldo likely, as always, to neglect his defensive responsibilities.
With both sides boasting their greatest strength down their respective left flanks, the opposite wing becomes an intriguing zone. Where Blaszczykowski will likely focus on ensuring Lukas Piszczek receives support for the difficult task of marking Ronaldo, Angel Di Maria might have freedom. This is often the case in Real Madrid matches - teams become overly concerned about Ronaldo, and neglect the threat posed by the agile and quick Argentine. He will test Marcel Schmelzer's willingness to go forward by driving forward on the counter-attack and dribbling directly on goal.
It's important to remember that for all that this game will be centred around transitions, both sides will experience periods where they will have to defend for long periods. Whichever team can press more as a unit and keep their shape compact will enjoy success - and so therefore, whichever one of the Germans can find space between the lines will be crucial. Ozil will drift wide, Götze will drift more vertically - before the latter joins Toni Kroos at Bayern, this is the last opportunity to see how Germany's three world class playmakers operate in their own environments.