On 9 August 2016, Casilla was in goal for injured Navas in the 3–2 victory against fellow Spaniards Sevilla for the UEFA Super Cup, in Trondheim. He managed to contribute more in his second year, and the club won the national championship after a five-year wait. His Champions League input consisted of the 2–1 group phase defeat of Sporting CP, as they again emerged victorious in the competition.