The Saudi-based star left international duty after Portugal coach Jorge Jesus addressed his decision to leave the 41-year-old as an unused substitute against Norway.
The five-time Ballon d’Or winner subsequently issued a statement promising to explain the reasons behind his departure “in due time” to the Portuguese public.
His decision has sparked mixed reactions, with some criticizing his actions while others have rallied behind the veteran forward.
Marcelo appears to be among those supporting his former Real Madrid teammate.
The Brazilian, who developed a close friendship with Ronaldo during their successful years together in Madrid, posted a picture on Instagram showing the pair embracing with the caption “What can I say, Cristiano Ronaldo?"