After lastnight's debacle, tonight's contest between the two best teams in Europe ought to be refreshing.
Barca's 5-0 win in the league at the Nou Camp is receding into memory, as impressive as it was. While it provided the platform for Barca to romp home in the league, it also provided Mourinho with food for thought, and in the two recent games, he has implemented a far more effective plan for dealing with Barca's burgeoning ability.
In the 1-1 draw at the Bernebeau, Real came back to win a point despite being a man down. In 120 minutes at the Mestalla in the Copa del Rey final, they kept Barca out, and Cristiano Ronaldo's fine header won the cup.
In both games, Barca have been on top for significant periods. And yet they only broke through once, and that a penalty.
They are not playing as freely as they did in that 5-0 win. That was never likely to be the case, because this stage of the season brings a heightened pressure which makes it harder to play expansive football. They will, of course, commot to their unique brand of attacking, but they need to find a cutting edge to slice through that dogged Madrid backline.
The tie against Arsenal showed their weaknesses almost as well as it did Arsenal's. With Barca so superior, in the second leg in particular, how did they come within a cunthair of being knocked out by a late Arsenal goal?
They were wasteful in front of goal over both legs and they simply cannot afford to replicate that against a team that will not give them as many chances.
There is also a popular argument at the moment that Pep Guardiola has mismanaged his squad. He does not have the strength in depth that Mourinho's team boasts, but in what many argue to be a relatively easy domestic league, he has failed to give Messi, or some of his other star players, much of a rest. Some say that this may be contributing to the team's less spectacular performances as the season goes on.
In a way, it's a match between two teams who are good defensively, while not having particularly good defences. Barcelona defend by keeping the ball, but when their teams do manage to get at them (which is pretty rare) they can be opened up on the break. Mourinho's Inter did this brilliantly in the first leg of last year's semi-final.
Recently, Mourinho has found some extra solidity by using the centre back Pepe as a destructive presence in midfield, sacrificing the more refined qualities of Mesut Ozil. Ozil played, and was little more than a spectator, in the 5-0 defeat. That game exposed the inadequacies of some of Real's defenders. Sergio Ramos is unconvincing, and Marcelo is better on the attack than in his own penalty area. Even the usually unflappable Carvalho looked flustered and lost.
But nearly all defenders prefer to defend deep, not leaving spaces in behind for speedy attackers to exploit. After that humiliation, Mourinho will never again attempt to play a high line against Barcelona. With Khedira injured, he'll bring Lassana Diarra in, and Madrid will look to fill the space in front of their own back four, cutting off the supply line of short, incisive passes between Barca's interchanging front five.
Can Barca use the wide areas effectively? Zlatan Ibrahimovic was turfed out because he impacted on Barca's ability to press as a unit in all areas of the pitch, and also because he was so disappointing over those two legs against Inter. Now, in his absence, they again lack a tall, physical presence up front, and are unlikely to score from a high cross into the area. So Real will look to defend narrow, and push Barca into playing the ball wide.
It should be a fascinating tussle between two contrasting philosophies.