Ronaldo has become one of the all-time greats of football since leaving Sporting to join Manchester United as a teenager in 2003.
The Portugal captain was a revelation at Real Madrid after leaving the Red Devils in 2009, breaking the LaLiga giant's all-time scoring record with a tally of 450 goals.
Ronaldo joined Juventus three years ago and, with his contract due to expire in 2022, the 36-year-old's future has been the subject of speculation as Andrea Pirlo's side are in danger of missing out on UEFA Champions League football next season.
The five-time Ballon d'Or winner's mother, Dolores, hopes her son can help Sporting add further honours after sealing its first Primeira Liga title in 19 years.
"I will talk to him and try to convince him to return next year," she was filmed saying by local station TVI 24. "To the Alvalade Stadium and to wear the colours of Sporting."
However, Mendes has poured cold water on the speculation and said Ronaldo has no plans to return to his homeland just yet.
"Cristiano is proud of the title won by Sporting, as he has publicly demonstrated," Mendes told Record. "But at the moment his career plans do not go through Portugal."
Ronaldo scored his 100th Juve goal in a 3-1 Serie A victory at Sassuolo on Thursday (AEST).