It's an uphill battle for Los Blancos, but the comeback kings will give it a chance. They need to win by three goals to force extra time, while a four-goal win or better will see them through to the last four. Scoring early will be pivitol, but even a two-goal victory won't be enough.

In Wednesday's other quarterfinal first leg, Paris Saint-Germain overcame a 1-0 deficit to English Premier League club Aston Villa at the Parc des Princes en route to a 2-1 victory. The decisive rematches will be played next week in Dortmund and Birmingham, respectively. Here are three quick takeaways following Wednesday's games.

The Premier League season is edging toward its climax, but how can clubs qualify for the Champions League, Europa League and Conference League?