It's the big one. It's the El Clasico. It's Mourinho vs Guardiola. Who will take a step closer to the Champions League final?
As only a brave man would bet against Manchester United making it to the Final at Wembley following their 2-0 first-leg win against Schalke on Tuesday, the question remains - who will join Sir Alex Ferguson's men in the showdown to be crowned Kings of Europe on 28 May?
Will it be Jose Mourinho's Real Madrid or the mighty Barcelona?
The Los Blancos have every reason to be confident ahead of the first-leg at the Santiago Bernabeu, having beaten the Catalan giants 1-0 to clinch the Copa del Rey last week.
But despite that and the home support that comes with it, Madrid defender Sergio Ramos insists his side aren't the favourites ahead of the
"We don't regard ourselves as favourites because I don´t think it serves for anything. If anything has led to success it's been simplicity, humility and hard work. And those are the values we must uphold," he said on his club's website.
"Both Barcelona and Real Madrid have great players and nobody can predict what will happen. We all know the responsibility we have and what it takes to defend these colours and we know we have to give it everything."
Meanwhile, Barcelona coach Pep Guardiola has launched a sensational attack on opposite number Mourinho ahead of the match on Wednesday.
He said: "Tomorrow [Wednesday] at 8.45 we will meet each other on the pitch. Off the pitch he has already won.
"In this room (press room), he's the f*****g chief, the f*****g man, the person who knows everything about the world and I don't want to compete with him at all.
"It's a type of game I'm not going to play because I don't know how.
"I won't justify my words. I congratulated Madrid for the cup that they won deservedly on the pitch and against a team that I represent and of which I feel very proud."
He added: "Off the pitch, he has already won, as he has done all year.
"On the pitch, we'll see what happens."
Real Madrid vs Barcelona: Key Battles
We look at which match-ups could shape the Champions League semi-final first leg between Real Madrid and Barcelona.
With Barcelona set to claim this season's La Liga title, and Real Madrid having got one over their bitter rivals with a win in the Copa del Rey final, this Champions League semi-final is the best opportunity for either team to assert their superiority over the other.So, which side will put one foot into the final at Wembley on May 26?
Gonzalo Higuain vs Gerard Pique
Fresh from a hat-trick at third-placed Valencia over the weekend, Higuain showed why despite the abundance of attacking talent at the Santiago Bernabeu, he is still coach Jose Mourinho's first choice striker.
The Argentinian is deceptively fast, but his greatest strength lies in his movement and his finishing ability. Higuain has an uncanny knack of drifting away from his marker unnoticed, before taking up excellent positions in the box. When his team-mates find him with a pass, he has the composure needed to finish.
This is why it will be imperative that Pique does not let the Argentine hitman out of his sight. The Spanish centre-back has established himself as one of the best defenders in the world since arriving at the Nou Camp with his strength and ball-playing ability.
However, his only drawback is his lapses in concentration in times, and he can be troubled by the niftiest of strikers. Keep an eye out on Higuain for 90 minutes, and it will go a long way in helping Victor Valdes keep a clean sheet. Let Higuain out of his sights for just a moment, and Barca may find themselves chasing the game.
Xabi Alonso vs Xavi
The battle of the midfield generals. Xabi Alonso vs Xavi will be a captivating duel in the middle of the park.
Alonso normally has his way in his holding midfield position, with the likes of Sami Khedira and Lassana Diarra winning the ball, before handing it off to him to initiate proceedings. However, you get the feeling Alonso will need to do his fair share of defensive work opposite Xavi.
Xavi is easily one of the greatest midfielders of his generation. He rarely looks in a hurry, but he never delays when he sees an opening, and his incisive passes more often than not lead to goals for the likes of Messi and company.
This may not exactly be a direct duel in the middle of the park between Alonso and Xavi. But in what is likely to be a creative head-to-head, whoever gets more of the ball will get increased opportunities to put their vision and passing ability to full use.
Cristiano Ronaldo vs Dani Alves
It's always difficult to pinpoint who Ronaldo's direct opponent will be. The truth is, he normally does not have one.
His movement between both flanks and through the centre, as well as the free role afforded to him by Mourinho means it is almost impossible to man-mark him. However, make no mistake that the Portuguese star will play on the left flank at some point of time during the match. And that could bring him face to face with Barca's right-back Dani Alves.
It is no secret that Alves definitely prefers to attack more than defend, and for good reason. He has great pace, dribbling prowess, and the ability to whip in a delightful cross for his forward to feed on. However, his ability going forward has masked the fact that in recent time, he has improved his defending.
Still, Alves is prone to having the odd iffy moment. In the quarter-final of the competition, he twice played in Shakhtar attackers with under-hit back passes. On both occasions, Valdes recovered to negate the danger. Do that again on Wednesday night, and Alves can be sure Ronaldo will punish him.
Iker Casillas vs Lionel Messi
It does seem odd matching up a forward against a goalkeeper, especially when you expect someone like Ricardo Carvalho to spend more time against Messi.
However, no matter how tight a leash Carvalho and his colleagues at the back keep Messi on, you cannot deny that the Argentine is going to have a few shots on goal and test the keeper.
Which means there will be a number of occasions where the only thing standing between Messi and putting the ball in the back of the Real net, is Iker Casillas.
Though not a conventional forward, Messi scores so many goals quite simply because he is a deadly finisher. From any angle, on either foot. He rarely powers the ball into the back of the net with venom. Instead, he caresses the ball into all four corners of the goal.
But Casillas is not just any regular goalkeeper. Over the past decade, he has time and again exhibited his full array of goalkeeping abilities. Superhuman reflexes, excellent covering of angles, and an alertness to rush out of his goal when he senses danger.
