The 24-year-old has been blighted by a succession of problems since his ¬£25million move from FC Porto in 2007 and there are now fears Ferguson will discard the South American as he looks to reinforce his midfield during the summer.
"He hasn't really realised his potential, which is there for all to see," said Ferguson.
"He is a fantastic footballer. I just hope he doesn't have the bad luck that Michael Owen has had throughout his career.
"At 23, obviously he's still very young and I'm sure we will get the benefit of that."