Seeing as Ozil took off to Arsenal, I would probably go with Isco. he is a bit too selfish now but if he can iron that out he can become the second best player.
Well look, he has to show off his worth in a galacticos team (he had to fight with Bale, Di Maria, Modric, Benzama , Jesse , Rodriguez... to start) , whenever he is given chance from bench ... I do not blame him for that, as long as he can make it more fruitful ...
I believe Isco could be the best player in the world some day, he is finding it hard to break into Ancelotti's 4-3-3 formation at the moment but none the less Madrid has a true genius in their ranks. I still would not call him Madrid's second best player, I still think it's a healthy Xabi Alonso, at the moment since he is not 100% healthy I'd say it was Di Maria until he got relegated to the bench by Bale, also believe or not Khedira was extremely important for the formation Madrid was running but now he's injured so I'd say it's Pepe, very important in the back line.