The Brazil international joined the Red Devils from Porto in 2007 but has failed to establish himself as a regular starter.
When asked if he could return to Portugal, the 24-year-old admitted he wants to leave Old Trafford but he remains under contract.
He told Globo Esporte: "What can I say? I have three more years of contract, I have tried to leave many times and never succeeded to do so."
While he would like to play for the Brazil national team again - his last appearance was back in 2008 - he is focused on the club's second leg against Real Madrid in the UEFA Champions League, as well as United's relentless push towards regaining the Premier League crown.
He added: "The national team is always good but we have to think about the second leg and about the English league."