At 16, Fati's Barca breakthrough has been the big LaLiga story this season.
But Denilson told AS: "I'm afraid they'll spoil him too much and forget that he's still a boy.
"Going fast is never good, do not burn the steps. He is a good player, but after his great debut, the hard times will come. And then, we will see how this situation will be managed and how he and his entourage will behave. It's not easy at his age.
"Sincerely, we must be careful."