The 21-year-old, who joined United in 2008 alongside his twin brother Rafael, has struggled to command a regular place at Old Trafford.
He has started just eight league games for the club, while his brother has over 40 starts to his name.
Red Devils manager Sir Alex Ferguson has confirmed Fabio, who usually plays on the opposite flank to his brother despite also being right-footed, is set to spend next season out on loan.
Reports suggest United are locked in talks to sign Benfica midfield star Nicolas Gaitan and as part of that will send a couple of players in the opposite direction, one of whom looks to be Fabio.
And his agent Cassiano Pereira has confirmed that there have already been discussions with Ferguson.
"There is a high possibility that Fabio will go to Benfica," he told O Jogo.
"Alex Ferguson has talked with me and Fabio about this possibility and the next two to three weeks we should know our position."