The 32-year-old striker picked up his fifth Ballon d'Or last week despite failing to meet his usual standards so far this season. For that reason, using statistics from domestic games only, Football Observatory have not included Ronaldo in their list of top 10 performing strikers.
A complex formula that takes into account chance creation, distribution and shooting to determine the most effective players in each position has left Ronaldo out of the top 10 with Sergio Aguero topping the charts.
"According to our algorithm Ronaldo was only the 12th best centre forward in the big 5 so far this season, and second in Spain after Rodrigo (but ahead of Suárez)," Dr Raffaele Poli, who heads the Football Observatory, told Business Insider.
For strikers, attributes such as taking on an opponent, creating chances, and shooting were all assessed, amongst other skills. Bayern Munich star Robert Lewandowski comes in second while Lazio's Ciro Immobile is third.
Ronaldo has scored just four La Liga goals this season out of a mammoth 57 shots on goal. Aguero, on the other hand, has scored 11 goals from 30 shots.