"Of course we miss Cristiano, but that's in the past now," Casemiro told reporters after his side were overpowered by their city rivals in extra time in Tallinn in coach Julen Lopetegui's first match since succeeding Zinedine Zidane.
"We cannot talk about Cristiano to cover things up, because any team would miss Cristiano. We are upset about losing a trophy but this is just the start. We have total confidence in our coach and giving excuses is not what Real Madrid do."
Real have not yet signed a replacement for the man who scored 451 goals and led them to four Champions League titles in the last five seasons.
The club received 105 million euros (£93.82 million) from Juve for Ronaldo in July, but the only new recruit at the Bernabeu has been goalkeeper Thibaut Courtois from Chelsea.
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Casemiro, however, said the loss to Atletico did not mean his side had to go out and make urgent signings.
"One result doesn't mean we have a better or worse squad, those in charge of the club will decide whether or not we need more signings," added the Brazilian.
(Reporting by Richard Martin; Editing by Christian Radnedge)
