It is tempting to look at the raw statistics and suggest that Barcelona and Bayern Munich both hoard possession above all, but the reality is that while for the former it is an ingrained philosophy, it is merely a reflection of Bayern's superiority in the Bundesliga. They are the closest anyone will come to out-possessing Barcelona, but while Barca will keep the ball for the sake of it, Bayern will attack efficiently and ruthlessly when they win the ball.
In that regard, it is likely that the battle for the ball between Europe's possession kings will fall the way of the leaders; but on the broader scale of the imminent war, it is far more difficult to predict a winner.
Having lost Mario Mandžukić to suspension, Jupp Hencykes must select a new striker. The hierarchy this season has generally seen Mario Gomez deputise in Mandžukić's absence, but Claudio Pizarro's recent good form has seen his stock rise, and Hencykes went on record this week saying he has "three first choice strikers" to choose from. Still, he will regret the loss of the Croatian, who plays a key role not only in terms of scoring goals, but also in setting the tone for Bayern's pressing, working energetically from the front to close down defenders.
He was handed responsibility for tracking the slippery Andrea Pirlo against Juventus and his replacement will have to do a similar job on Sergio Busquets. The Spanish midfielder typically plays a safe, short passing game, but showed against AC Milan he is capable of quick, positive distribution into the forward line.
That will be one element in what is set to be an engrossing midfield battle. The selection for either side is predictable: Bastian Schweinsteiger and Javi Martinez will be up against Xavi and Andres Iniesta. It will be intriguing to see how Bayern approach this zone, as their midfield pivot is capable of playing two roles - either sitting back and stifling their intricate play between the lines, or pushing up and trying to force the two Spaniards into turnovers. The latter seems more likely when considering how Bayern have approached games this season, with a relentless energy and intensity that has seen them swamp all before them in the Bundesliga.
The loss of Toni Kroos could be significant. The playmaker has become the hub at the heart of this Bayern team; able to play a variety of roles from the No. 10 position. His ability to drop deep into midfield - something he did excellently in last year's semi-final against Real Madrid - would have been useful here, to help retain possession and dictate the tempo of Bayern's passing. His replacement, Thomas Muller, is similarly talented, but operates in more advanced positions and less versatile with his movements. He will drift out towards the right flank, allowing Arjen Robben to cut inside and Phillip Lahm to overlap down the touchline.
Sergio Busquets is experienced and calm to deal with the threat of Robben cutting inside and will position himself slightly left-of-centre to cope, but it is Jordi Alba who might really struggle. There will be no Carlos Puyol, Javier Macherano or Adriano available to play in central defence, making it likely that youngster Marc Bartra will be called into the side. As Pique favours playing on the right hand side of a partnership, Bartra will likely be dragged out to the flank to help Alba deal with Bayern's overloads down the right. A Bayern goal from this side looks likely thanks to Phillip Lahm, who currently ranks equal first for assists in the league and will try to aim low crosses across the face of goal in search of midfield runners.
Barcelona's own attacking threat is predictable. Provided Messi starts -- and the latest rumours suggest he will -- the Argentine will play as a false nine, coming deep to collect possession and either dribbling directly on goal or feeding passes into the path of the inverted wingers.
It is likely that the two centre-backs will be responsible for tracking Messi when he moves in between the lines. Dante is an aggressive, pacy defender comfortable in coming off his line and so is well suited to this task, but his partner of recent weeks, Daniel Van Buyten, lacks this mobility. With that in mind, it would be unlikely, but not surprising to see Jerome Boateng start inside. He's a more mobile defender, more comfortable tracking Messi in deep positions, and shares a good understanding with Dante, especially knowing when to drop deep and cover if the Brazilian charges forward.
Meanwhile, on the Barca flanks, Pedro will almost certainly start. He times his runs from the right flank into the penalty box expertly, so David Alaba must be wary of his movement. On the opposite side, it will be either Alexis Sanchez or David Villa performing a similar role. With the threat of Bayern's wingers on the counter-attack ever present, there may be little opportunity for Dani Alves and Alba to get forward and provide width, making it crucial for Barcelona that whoever starts on the left is firing on all cylinders.