Mourinho can get some very important points out of this game whenever he's able to watch it again. First of all, Ramos should never be considered as a potential starting right back with a healthy Arbeloa. Second, Essien can't play against European's top teams in the left wing. He was the best player against Celta, but needless to say Champions League isn't the same story.
Furthermore, Casillas has not completed a perfect game for quite a long time. Even though he did save some chances by Dortmund, the first goal hits the back of the net through the post he's supposed to be guarding and the second one comes after a very bad aerial clearance. Everybody knows that he's not going to improve that part of his game, but now the question is: Can you win a Champions League title with that kind of performance in the aerial football?
Borussia Dortmund wasn't impressive. They worked a lot to prevent Real Madrid from getting into its usual playing rhythm, but their two goals come off Real Madrid's mistakes. Period. First, Pepe tried to find Özil, but Lewandowski reached the ball and scored through Casillas' good side. Pepe had a brilliant game defensively but was very uncomfortable with the ball on his feet and had tons of turnovers. Real Madrid's only good defender was Varane. This french kid is going to be Real Madrid's starting center back soon enough. He should, anyway.
Unfortunately for Real Madrid, Sami Khedira, who returned to the starting lineup, had to leave the game in the 20th minute. He should miss two or three more weeks. Modric entered the pitch. The Croatian is a very different player, and it's obvious that Real Madrid missed Khedira's physical presence. This is the tougher stadium in Europe and a Modric-Alonso midfield is not enough to contain the German champions.
Real Madrid tied the game up soon after Lewandowski's goal off a brilliant assist by Mesut Özil and a first-touch chip by Cristiano Ronaldo. Özil played one of his most complete games of this current season, but Ronaldo couldn't be a part of the team's play at any time. Benzema was invisible once again, and Real Madrid needs either him or Higuaín to step it up soon.
Di María performed terribly in the first half. He couldn't do a thing right, but he raised his level in the second half of the match, and so did Modric. Real Madrid's lack of options in the bench forced Mourinho to finish the game without making the three allowed changes. He removed Benzema for Higuaín, but neither Callejón nor Kaká could've likely made an impact against Dortmund.
The refereeing was one of the worst ever seen in European football. He's not to blame for Real Madrid's loss, but he didn't call a single Borussia foul on Mesut Özil. The German player was crowded every time he touched the ball, and the German defenders fouled him most of the time. Ramos and Alonso saw yellow cards the first time they fouled, though, while Hummels got away with a very dangerous tackle to Özil. Westfallenstadion's crowd plays a big factor in this, probably. Dortmund has a great crowd that is on the referee's back during the whole 90 minutes. Again, the referee didn't give the win to Dortmund, but seeing the German team walk away without getting a true yellow card (Gundogan saw one in the 92nd minute) can only be seen as a joke.
Given Manchester City's failure against Ajax, Borussia Dortmund now leads the group with 7 points. Jose Mourinho's Real Madrid has 6, while Ajax and City are well behind with 3 and 1 respectively. That means that Real Madrid's next Champions League game against Dortmund in the Santiago Bernabéu will be crucial.