Although he was supposed to be out of the fields just for three weeks, further examinations might have shown that Álvaro's injury is more serious than it was thought to be and he would need two months to recover.
If that were true, it would mean that he would not be able to participate in the Copa del Rey final, the final legs of the Champions League or the last games in La Liga, and Carvajal would be our only possible choice for the right fullback. Moreover, his chances of arriving in good shape to take part in the World Cup would be drastically reduced, given also that he was not called by Vicente del Bosque to the last friendly game against Italy.
Carlo Ancelotti will lose a lot of depth for his defensive line, and Nacho Fernández could be Carvajal's backup for these two months. Sergio Ramos could also play the position.