The striker is yet to start a LaLiga match for Barca since his August arrival from Borussia Dortmund, with coach Ernesto Valverde admitting yesterday his defensive game needs to be improved.
However, Desailly insists Dembele will make it at the Nou Camp.
He said, "In 3, 4 or 5 years, (Andres) Iniesta will leave. At that moment, Ousmane Dembélé will be there. He's a bet for the future. Barcelona was able to detect his potential, we should not hurry with him.
"You have to let him grow, step by step. He is without a doubt one of the best young talents in the world. His true value is immense. He is versatile, he destabilises the opponent, he will do a lot of good in Barcelona and the team of France.
"He has everything to get to the best level, he's a craque."