The Romanian played alongside the current Paris Saint-Germain striker at Juve between 2004 and 2006 and often shared a room with the Swede for away games.
"It is hard to say who has been the most talented player I teamed up with. If I have to mention one, I would have to go with Ibrahimovic," Mutu told Costin Desliu.
"He was my room-mate at Juventus and I once woke up in the middle of the night. [He said:] 'Adi, wake up, I had a nightmare. I dreamed that Ronaldo is better than me.'
"I told him to calm down and assured him that he was the best around.
"He always kept on working to improve himself. I have met few players who are as passionate as Ibrahimovic."
Mutu fails to specify whether it was Brazilian legend Ronaldo haunting Ibrahimovic at night or if it was current Real Madrid star Cristiano Ronaldo.
Former Inter and AC Milan striker Ronaldo was a key figure at Madrid at the time, whereas Cristiano was in the early stages of his time at Manchester United.