Calderon insists Ronaldo hasn't been replaced since his move to Juventus.
He told CMIT TV: "The departure of Cristiano Ronaldo still weighs heavily, as Real have failed to fill the offensive void left by the Portuguese.
"Therefore, an attacker able to cover this role is needed. Real Madrid have failed to do so in recent years, and it has mostly been seen in the Champions League.
"Personally, it took me two years to convince Cristiano Ronaldo to come to Real Madrid and then we were happy for nine years. Now Real needs someone who has the pace and quality of Cristiano Ronaldo."