The Spanish Under-21 international has enjoyed a breakthrough season at the Bernabeu, scoring eight times in all competitions for Los Blancos.
"I want to send a lot of encouragement to Jese," Ronaldo told reporters.
"He had become a very important player to us and always did well when he played. He will be important for us again in future but the truth is it is very bad news for him and for the locker room."
Ronaldo scored twice in the victory over Schalke, which secured Madrid's spot in the quarter-finals of the competition.