Ronaldo, whose contract with reigning Serie A champions Juventus is set to expire at the end of the 2021/22 campaign, has been strongly linked with a return to Los Blancos, where he previously scored a club-record 450 goals in just 438 matches.
However, former Brazil international Rivaldo has warned the five-time Ballon d'Or winner to think carefully about his next move and that a return to the Santiago Bernabeu could ruin his remarkable legacy at the club.
"There's a lot of talk about Cristiano Ronaldo leaving Juventus at the end of the season after the Italian giants were knocked out of the Champions League, with a return to Madrid mooted in the press," Rivaldo wrote in his latest Betfair column.
"For me, this will always depend on Cristiano and his plans for the future. He is a Madrid idol and I believe that Madrid fans would be very happy to have him back. But we must recognize that Ronaldo isn't the same player from three seasons ago.
"He will continue to score many goals and make the difference proving his great determination on the pitch, but if he goes back there's the risk that Madrid fans will demand too much from him at this phase of his career.
"If things didn't go well, and the club failed to have success with him in their ranks, his status could suffer. So a return to Spain comes with risks."
Ronaldo has also been linked with a move to Manchester United, Paris Saint-Germain and Inter Miami, although Juventus' managing director Fabio Paratici previously stressed that the 36-year-old will be staying in Turin.
"He's the best in the world and we're holding on to him," Paratici said following Juve's shock defeat to Benevento over the weekend, per CNN.
"The word transition doesn't exist at Juventus, we always play to win. Some seasons go better than others, but the word transition doesn't exist. Seasons are important even if they're about growth that yields results in the subsequent years."