The 23-year-old is said to be concerned about the amount of playing time he will get at Old Trafford this season, with Chris Smalling and Phil Jones also in contention for the right back position.
Brazilian giants Corinthians are said to be in the market for a right back, and see Rafael as the perfect replacement for retiring star Alessandro.
Rafael is yet to play this season after suffering an injury, but is believed to be close to a return to full fitness.
The Brazilian was a regular first team fixture under Sir Alex Ferguson, but it is not yet known whether David Moyes sees him as first choice.
He is currently contracted to the club until 2016, although United would find it difficult to hang onto the young defender if he decides he wants to return to his homeland.
Rafael has continued to improve during his time at Old Trafford since arriving back in 2008.
He has made a total of 80 Premier League appearances for the current champions, and has scored five league goals, picking up three title winners medals in the process.
He has also won two senior caps for Brazil, and is looking to force his way into Luiz Felipe Scolari’s plans for next summers World Cup.