Stoichkov fears Ronaldo's ankle will now be targeted by opposition defenders after his setback last month.
"He's a great player like Figo was in his day, who scored before and after in Madrid. But injuries can kill you. In England they play with more nobility, they go more for the ball. In Spain it is different," said Stoichkov.
On Real coach Manuel Pellegrini, he added: "We'll see what happens with Pellegrini. The coaches do well or poorly through two things: the players and results. Madrid has much of the first and so far, little of the latter."