Mateo Kovacic is a Croatian midfielder who plays for Inter Milan. He's still 20 years old and has the potential to certainly dominate the position in the next few years. In fact, he's already starting for Inter Milan and is aiming to start for Croatia during the World Cup as well. While he can play as a deep playmaker -like Pirlo or Verratti-, he seems to be more comfortable as an attacking midfielder. But still, he could always get used to play deeper and develop the skills needed for that position.
Kovacic could be Real Madrid's plan B for the midfield, according to SportYou. They don't seem to have a lot of sources inside the club, but Kovacic could be a very interesting signing for Real Madrid's future because of his versatility. He's already a good playmaker who's learning how to improve tactically in the Serie A. If Inter are commited enough to make an effort for Morata, Real Madrid should try to ask for Kovacic in exchange.