For all the talk of El Clasico being the biggest club game in world football, there's an uncomfortable truth for Saturday's clash. Real Madrid will simply have to rest players ahead of facing Manchester United. There is no alternative - the Champions League is a far more winnable competition than La Liga at present, and United will have a much greater opportunity to rest players. Not only is their squad perfectly-built to allow them to do so, they are facing Norwich City, and hold a 12-point lead in the league. Combined with Real Madrid being behind on the tie in away goals, and needing to attack, fielding the same eleven on both days is simply not an option.
Fortunately, Barcelona will be in the same boat thanks to Milan handing them a shock defeat and Xavi being injured, so while it's possible that we're set for one of the most tense, hushes Clasicos in recent years, it rarely happens in reality. The occasion proves too much for any real notions of discipline or taking it easy, and in any case, Barcelona have little scope to rotate. Because of that, Real Madrid's squad ultimately gives them the advantage when the fixture list becomes tight. We've pointed out the flaws in Barcelona's transfer policy in recent years, but it's ultimately the inability to come up with a rotating system in midfield and attack that leaves them forced to field the same players in quick succession.
In contrast, Real Madrid may not be getting the best out of Luka Modric, and they always have to leave one of their best attacking players on the bench in Gonzalo Higuain and Karim Benzema, but it allows them to completely rest key players with virtually no drop-off in quality. Combined with generally more versatile players, it gives Mourinho the tools necessary to do the part of his job when good managers really prove their worth - squad rotation in a period of fixture congestion where there is little margin for error.
This is, then, not only why players like Luka Modric were signed, but also why José Mourinho was appointed. This is where a great manager can really make the difference - the eye-poking, suit-ruining, medal-throwing smokescreen is exactly that - his team requires no motivation against Barcelona or at Old Trafford. It's in the minutiae of team selection where the battle will be won - and that's precisely where Madrid have the upper hand, against Barcelona at least.
His opposite number at Old Trafford has long mastered the art, even permitting himself some bizarre team selections in the league. When it comes to the big games, he invariably gets it right, as he proved in Madrid by starting Danny Welbeck. The two games will be instrumental in defining José Mourinho's legacy at Real Madrid, but for all their recent brilliance, they are in a bad position. Barcelona look unassailable, and United have the upper hand. Fortunately, in the event of victories against the odds, football history has a convenient tendency of overlooking how a team ended up in such an unfavourable position in the first place. They may only be needing a miracle due to self-sabotage, but it will only mean more glory if they pull it off.