Navas said Ronaldo left Real Madrid with a big hole to fill.
Navas was part of the side that suffered a shock 1-0 defeat to CSKA Moscow in the Champions League last night.
The Russian outfit beat the reigning champions 1-0 despite Los Blancos having won the competition for the previous three seasons.
Ronaldo departed as Real Madrid’s all-time leading goalscorer with Julen Lopetegui’s side having now gone three games in a row without scoring.
Real Madrid last endured such a goalless streak in January 2007 under Fabio Capello – before Ronaldo had joined the club from Manchester United
And Navas has admitted Ronaldo has left a big hole at the Bernabeu but is determined to move on.
“Cristiano left the bar very high at Real Madrid,” Navas said.
“You cannot cover the sun with a finger.
“He made many goals while he was here, but it’s already the past and we cannot live in the past.”