The player's representative has jokingly claimed his client would be even more prolific if he played at Camp Nou
The Portuguese has scored 69 goals in 2013 - a tally superior than any other player on the planet and 24 more than Messi's total of 45 over the same 12-month period.
"Messi's goalscoring record? If Ronaldo played for Barcelona he would score 120 goals a season," Mendes told A Bola TV.
Ronaldo will battle it out with Messi and Franck Ribery for the Ballon d'Or, with the winner of the prize set to be announced on January 13.
The Madrid star is the favourite with bookmakers to land the trophy for the second time in his career after he was crowned the world's best player in 2008 during his time with Manchester United.
The 28-year-old has scored 18 goals in just 16 Liga appearances this season and recently made his return to action after a brief spell on the sidelines with a hamstring injury.