The 3-0 win went some way to ending the disappointment of their Champions League elimination last week.
"It was important to win today after the harsh blow of losing on Wednesday in a penalty shootout at our stadium. We have to look ahead and focus on winning this league title, which we are all excited about and would be a beautiful thing. We've topped the table for most of the season," said Casillas.
"We had to defeat Sevilla and we did. We've taken a solid step in the championship and winning the title would be a reward to the hard work we've been doing for months, even years. This project has to start showing success. We'll have to wait until we mathematically win."