Signed from Fluminense in 2008, the pair have spent their careers together and both believe United need to be positive.
Rafael told The Guardian: 'I don't see why we can't hurt them if we stick to a game plan where we don't make the same mistakes made by some of their opponents. Basically, Barcelona do not like being attacked or pressured. We need to make them feel uncomfortable.'
Fabio added: 'We have a side full of confidence and good players and shouldn't fear Barcelona.'
Since arriving at Old Trafford at the age of 17, the pair have gradually progressed and become part of the United fold under the watchful eye of Sir Alex Ferguson, a man Fabio trusts and respects, despite being confused for his twin by the Scot on occasions.
'Sir Alex knows everything about football and he loves the Brazilian style. He is crazy about Cafu, our idol,' added Fabio.
'There was a match where he came to me in the dressing room and started to tell me off, but calling me Rafael. He still gets us confused, but it doesn't matter.'
His twin is equally respectful of the 69-year-old boss and recalls a moment in the changing room after the Brazilian’s crucial sending off against Bayern Munich in 2010.
Rafael said: 'He was angry but it was more a paternal dressing-down than anything at full blast. It actually made me feel more ashamed than if he had screamed. But he always talks to us about taking time to learn with our mistakes and not being too anxious.'
Despite amassing more Premier League playing time on the pitch than his brother this term, Rafael is expected to watch on from the sidelines as his twin pushes for the starting XI on Saturday after a strong finish to the season in United’s run-in.
'I am happy to see my brother bouncing back after a difficult start at United,' added Rafael.
'He got injured a few times and didn't get many games in the first two seasons. There was even talk about him being loaned out. We have been together throughout our entire career and would love to keep it this way for as long as possible.'
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