"This chapter is over," Ronaldo cryptically said on social media with a photo of him in an Al-Nassr shirt.
Ronaldo, the top scorer in this season's Saudi Pro League, has eight in seven appearances in this campaign's Champions League Elite, one short of joint-top scorers Riyad Mahrez, Salem Al-Dawsari, Anderson and Jasir Asani.
The 19-year-old forward, who trains daily alongside one of football’s all-time greats, is part of a promising Saudi Arabian generation aiming to make a statement on the global stage.
Al-Nassr remain in the third place with 54 points but they are now three points behind second-placed Al-Hilal and seven off leaders Al-Ittihad, who visit Al-Ahli on Saturday.
Cristiano Ronaldo's Saudi side Al Nassr were on Monday drawn against last season's runners-up Yokohama F-Marinos of Japan in the quarter-finals of the Asian Champions League.
Ronaldo, the Al Nassr captain, was reportedly rested for last week's goalless draw in the first leg in Iran, however returned to lead the side at Al Awwal Park.
Ronaldo turned 40 last week with his current contract due to end in June 2025.
Al Nassr captain Ronaldo had looked destined to endure a hugely frustrating game following a series of missed opportunities in the first half at Al Bayt Stadium.
The Portuguese star, without a goal in his past three appearances for the Saudi Arabian side, netted the second of the hosts' goals at Al Awwal Park in Riyadh.
World Cup-winning French midfielder N'Golo Kante has signed a three-year deal with Saudi Arabia's Al-Ittihad, a club source told AFP on Wednesday, a day after Real Madrid striker Karim Benzema also joined the team.
PSG will take on Saudi side Al Nassr in Osaka on July 25 and J-League club Cerezo Osaka three days later.
The Portuguese forward decided not to sit on the bench for the frustrating end to his first season in Saudi Arabia after joining Al-Nassr in January on a contract estimated by the media to be worth more than 200 million euros ($213.5 million)
"Step-by-step I think this league will be among the top five leagues in the world but they need time, players and infrastructure," said Ronaldo
Saudi Arabia and Al-Hilal defender Ali Al-Bulayhi joked he is afraid Lionel Messi will ask for his departure if the Argentine forward joins the Saudi club, after an argument with him during a World Cup match last year.
Al-Hilal president Fahd Bin Nafel refused to comment on the possibility of signing Lionel Messi, insisting his Saudi Arabian side is "more important than just one player", as fans clamour for the World Cup winner.
Al Nassr star Cristiano Ronaldo was gifted a custom-made watch as he attended the Jacob & Co boutique launch in Saudi Arabia.
Portuguese striker Ronaldo thought he had given his team the lead in the 58th minute only for the referee to cancel the goal for offside
Brazilian legend Rivaldo suspects that Cristiano Ronaldo was “fooled by the big contract in Saudi Arabia” and advises the Portuguese megastar to “return to Real Madrid to finish his career”.
Cristiano Ronaldo brought out the fierce competitor in him on Tuesday but his efforts were in vain as Al-Nassr failed to score in two consecutive fixtures in the Saudi Pro League and suffered a 2-0 defeat away at Al-Hilal.
