The Brazilian arrived at Old Trafford for £52million over the summer, but he is yet to make his mark in the team, something which Gilberto thinks he can change.
"I am confident he will do well at United," the former Arsenal player said.
"He is a strong character and he has shown that in the past. There is a huge difference between life in Brazil and in the Ukraine but Fred adapted well. He will also adapt at Old Trafford in time.
"I speak with him regularly and it was always his wish to come to England if he left the Ukraine.
"It takes time to get used to football in England. It was hard for me when I first came to Arsenal from Brazil. Everything is different. The pace and the tempo of game. The intensity. It is so different to Brazil. For Fred, it will also be different than in the Ukraine."