Ronaldo, who played for Barca in the 1990s, believes that the Argentina international will claim his fifth award when it is handed out in the New Year.
"I think Messi will win the Ballon d'Or again," Ronaldo told Marca
"Messi has spent the last five years playing so many matches and he is the biggest star in world football.
"Now, this injury isn't serious, but maybe resting will allow him to recharge his batteries."
The Brazilian won the award himself twice in 1997 and 2002.