Rivaldo refused to rule out the possibility of former Barcelona star Neymar joining bitter Spanish rivals Real Madrid.
Neymar left Barca for French giants Paris Saint-Germain in a world-record EUR222million deal in August but the Brazil international has been linked with Madrid.
Madrid captain Sergio Ramos has previously insisted Neymar would be welcome at the LaLiga and Champions League titleholders, while president Florentino Perez fuelled rumours after claiming the PSG forward would have a better chance of winning the Ballon d'Or in the Spanish capital.
Asked about Neymar's future and Madrid during a commercial event, ex-Barca star Rivaldo said: "You never know what can happen in his future."
Neymar finished third in this year's Ballon d'Or as Cristiano Ronaldo claimed a record-equalling fifth award to move level with Barca foe Lionel Messi.
Brazilian great Rivaldo - who won two LaLiga titles, the Champions League and the World Cup during his illustrious career - insisted he could challenge Ronaldo and Messi for the Ballon d'Or if he was still playing.
"If Ronaldo won is because he deserved it," the 45-year-old said.
"In my time, there were more players than today challenging for being the best in the world, I remember Figo, [Alessandro] Del Piero or [Francesco] Totti, now you always hear about the same players and I am pretty sure I could challenge with Messi and Ronaldo because football was harder in my times.
"I am not here for opening a controversial [laughs], I just say both are very good players but in my times you could find more quality players than today, in which you only hear about Messi, Ronaldo and Neymar."