Time for another brief foray away from writing about Liverpool. This is how I think Madrid and Barcelona will line up tonight:
Khedira and Carvalho are unavailable for Real Madrid. This would normally mean that Albiol would come into central defence, but I am not convinced that Mourinho trusts him. Remember he was sent off in the most recent league meeting between these two sides. As a result, I think Pepe will drop into the centre-back position, vacating the defensive-midfield role he has filled so well in recent weeks. This allows for a slight reconfiguration of the Madrid line-up, bringing in the disciplined Diarra in place of the comparatively energetic and impetuous Khedira, and reverting to their usual formation for home matches - 4-2-3-1.
Mourinho had moderate success fielding three defensive midfielders against Barcelona in their previous two meetings - the 1-1 draw at the Bernabeu in the league (Madrid claiming an equaliser with 10 men), and the 1-0 AET Copa del Rey final victory - and will have learnt some important lessons from the way that his side was humiliated in the away league fixture earlier in the season when they fielded a more offensive side. So why would he risk getting soundly beaten again when his defensive line-ups have had more success?
For one, it's a matter of strategy for Mourinho. Like when his Inter side faced Barcelona at this stage of last season's competition, he will probably want to go out and attack aggressively and energetically at home, in the hope of having a lead to defend when Madrid travel to Camp Nou.
And, although tactics aren't crucially distinct from strategy, there are more traditional tactical benefits to be noted. Firstly, the 4-2-3-1 makes it easier for Madrid to press Barcelona high up the pitch, in comparison with the comparatively passive 4-3-3 which would leave Busquets unattended in the centre. In addition, the above formation allows CR7 to be positioned on the right-wing where he can attempt to expose whoever Barcelona choose to play at left-back in the absence of their first three choices (Abidal, Adriano and Maxwell).