The former Spain striker claims the goalscoring exploits of the Portuguese and Lionel Messi are "crazy" but says you cannot compare them with past stars such as Alfredo Di Stefano.
The Portugal sensation recently surpassed Ferenc Puskas on the all-time scorers list for los Blancos and is now 46 goals short of former Spain international Santillana's tally of 289, having scored 42 goals in all competitions to date this season.
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While iconic striker Raul remains the club's record scorer with 323, Santillana is fully convinced Ronaldo will surpass his tally as he and Lionel Messi continue to set a new standard with their "crazy" performances on the pitch.
"Cristiano Ronaldo can reach them all. It's normal [for him]. At my time it was unthinkable for a player to hit 50 goals in a season," he told Goal. "What Messi and Ronaldo are doing is crazy. You have to enjoy it.
"Ronaldo will catch them all - first me, but then [Alfredo] Di Stefano, Raul, everyone. Madrid will benefit, with the goals, the points, the knockout games... He will break all records, I'm convinced."
Question marks remain over whether Ronaldo can be considered the greatest player in Madrid's illustrious history, but Santillana believes it is too difficult to compare the modern game with the past eras of the likes of Di Stefano.
"Is Ronaldo better than Di Stefano, when he scored more goals than him? You cannot say. You can't just use goals to compare players," he said. "Di Stefano was the best in his time, Ronaldo and Messi are the best in theirs.
"You have to look at the pitches we played on in my time, with rain, mud, marks, divets. In the European Cup there are many more games [now], in the past it was only the winners of the leagues... There are many things to consider."