For a club of Real Madrid's size, it's normal to keep an eye on the world's greatest prospects, and Raheem Sterling is one of them. Real Madrid Castilla coach Zinedine Zidane confirmed that the Liverpool star is on Real Madrid's radar.
We know who Raheem Sterling is, and of course we are monitoring him as a player. There are very few players in the world who can improve the Real Madrid squad, so it is going to make sense we monitor the progress of the best young players in the world. We monitored Bale for over a year, the same with Isco and also Raphael Varane. We monitor many of the best young players in Europe, then if we feel they have something to offer Real Madrid we will contact their club and try and make the next step.
This is not surprising and Zidane's words make a lot of sense. Sterling is currently in talks with Liverpool over a contract extension, so if Real Madrid are really interested in bringing him in, it could be a realistic option to add some depth to the current squad.