The 20-year-old winger spent last season on loan at Everton in order to gain first-team experience, making 29 appearances in all competitions.
The Toffees manager told Mundo Deportivo: "He is ready to play for Barcelona because he has special talent, certain qualities that make him stand out.
"I was delighted when [Vicente] Del Bosque called him up for the friendly before the World Cup. They had followed him for the year he was at Everton and were able to see that he was performing to a very high level.
"It would have been good for Gerard and for Everton if he had stayed for us for another year. He would have enjoyed a bigger role in the team than I think he will have at Barcelona because of the competition he will find there."
Deulofeu scored four goals during his spell with the Premier League club.