Ronaldo moved to the Middle East in December 2022, shortly after his contract with Manchester United was terminated by mutual agreement.
He became the highest-paid player in football history with an annual salary of £177 million.
However, ten-time league champions Al-Nassr have only won the 2023 Arab Club Champions Cup since joining.
He signed a new two-year contract last June, but BBC Sport was told his former Real Madrid team-mate Karim Benzema’s recent switch to league leaders Al-Hilal from Al-Ittihad was the main reason for five-time Ballon d’Or winner Ronaldo’s frustration.
Al-Hilal, who top the Saudi Pro League table with one point more than Al-Nassr in second place, are also managed by the PIF.